criyle/codenet-compile-errors huggingface dataset:
Language: C++

#include<bits/stdc++.h>

#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define endl "\n"
#define ll long long
#define pii pair<int,int>
#define all(x) begin(x), end(x)
#define loop(i,n) for(int i=0; i<n; i++)
#define rep(i,a,b,c) for(int i=a; i<b; i+=c)
#define brep(i,a,b,c) for(int i=a; i>b; i-=c)
#define tc(t) int t; cin>>t; while(t--)
#define sz(v) int((v).size())
#define pb push_back


using namespace std;

void __print(int x) {cout << x;}
void __print(long x) {cout << x;}
void __print(long long x) {std::cout << x;}
void __print(unsigned x) {std::cout << x;}
void __print(unsigned long x) {std::cout << x;}
void __print(unsigned long long x) {std::cout << x;}
void __print(float x) {std::cout << x;}
void __print(double x) {std::cout << x;}
void __print(long double x) {std::cout << x;}
void __print(char x) {cout << '\'' << x << '\'';}
void __print(const char *x) {cout << '\"' << x << '\"';}
void __print(const string &x) {cout << '\"' << x << '\"';}
void __print(bool x) {cout << (x ? "true" : "false");}
template<typename T, typename V>
void __print(const pair<T, V> &x) {cout << '{'; __print(x.first); cout << ','; __print(x.second); cout << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cout << '{'; for (auto &i : x) cout << (f++ ? "," : ""), __print(i); cout << "}";}
void _print() {cout << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cout << ", "; _print(v...);}
template <typename T> inline void inp(T &any) {cin >> any;} template <typename T, typename... U>inline void inp(T &a, U &...b) {cin >> a; inp(b...);}
#define rin(args...) ll args; inp(args);
#ifndef ONLINE_JUDGE
#define debug(x...) cout << "[" << #x << "] = ["; _print(x)
#define matdeb(mat,row,col) cout << #mat << "::" << endl; printmat(mat,row,col); printpartition;
#define debugv(v,n) cout << #v << ":" << endl; printv(v,0,n-1); printpartition;
#else
#define debug(x...)
#define matdeb(mat,row,col)
#define debugv(v,n)
#endif

const int maxm = 1000000000 + 7;

double startTime;
double getCurrentTime() {
	return ((double)clock() - startTime) / CLOCKS_PER_SEC;
}


//----------->CODE BEGINS --------------->


int main()
{

#ifndef ONLINE_JUDGE
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
#endif

	string s;
	cin >> s;
	string ans;

	rep(i,0,s.lenght(),2)
	{
		ans += s[i];
	}



  cout<<ans<<endl;



}


Compiler output:
a.cc: In function 'int main()':
a.cc:73:19: error: 'std::string' {aka 'class std::__cxx11::basic_string<char>'} has no member named 'lenght'; did you mean 'length'?
   73 |         rep(i,0,s.lenght(),2)
      |                   ^~~~~~
a.cc:9:37: note: in definition of macro 'rep'
    9 | #define rep(i,a,b,c) for(int i=a; i<b; i+=c)
      |                                     ^
Language: C++

#include <bits/stdc++.h>
using namespace std;

int main(){
  string S;cin>>S;
  int l=S.size();
  string ans=S.at(0);
  for(int i=2;i<l;i+=2) ans+=S.at(i);
  cout<<ans<<endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:7:18: error: conversion from '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'} to non-scalar type 'std::string' {aka 'std::__cxx11::basic_string<char>'} requested
    7 |   string ans=S.at(0);
      |              ~~~~^~~
Language: C++

#include <iostream>
#include <string>

int main()
{
  std::string s;
  std::cin >> s;
  
  for(int i = 1; s[i] != NULL; i++)
  {
    if(i % 2 %= 0)
    {
      std::cout << s[i];
    }
  }
  
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:9:26: warning: NULL used in arithmetic [-Wpointer-arith]
    9 |   for(int i = 1; s[i] != NULL; i++)
      |                          ^~~~
a.cc:11:14: warning: division by zero [-Wdiv-by-zero]
   11 |     if(i % 2 %= 0)
      |        ~~~~~~^~~~
a.cc:11:10: error: lvalue required as left operand of assignment
   11 |     if(i % 2 %= 0)
      |        ~~^~~
Language: C++

#include <iostream>
#include <string>

int main(void){
  string s; std::cin >> s;
  for(int i = 0; i < s.size(); i+= 2){
    std::cout << s[i];
  }
  std::cout << std::endl;
  return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:5:3: error: 'string' was not declared in this scope
    5 |   string s; std::cin >> s;
      |   ^~~~~~
a.cc:5:3: note: suggested alternatives:
In file included from /usr/include/c++/14/iosfwd:41,
                 from /usr/include/c++/14/ios:40,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stringfwd.h:77:33: note:   'std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
In file included from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44:
/usr/include/c++/14/string:76:11: note:   'std::pmr::string'
   76 |     using string    = basic_string<char>;
      |           ^~~~~~
a.cc:5:25: error: 's' was not declared in this scope
    5 |   string s; std::cin >> s;
      |                         ^
Language: C++

#inculde<iostream>
#include<string>

int main(void){
  string s; std::cin >> s;
  for(int i = 0; i < s.size(); i+= 2){
    std::cout << s[i];
  }
  std::cout << std::endl;
  return 0;
}

Compiler output:
a.cc:1:2: error: invalid preprocessing directive #inculde; did you mean #include?
    1 | #inculde<iostream>
      |  ^~~~~~~
      |  include
a.cc: In function 'int main()':
a.cc:5:3: error: 'string' was not declared in this scope
    5 |   string s; std::cin >> s;
      |   ^~~~~~
a.cc:5:3: note: suggested alternatives:
In file included from /usr/include/c++/14/string:41,
                 from a.cc:2:
/usr/include/c++/14/bits/stringfwd.h:77:33: note:   'std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
/usr/include/c++/14/string:76:11: note:   'std::pmr::string'
   76 |     using string    = basic_string<char>;
      |           ^~~~~~
a.cc:5:18: error: 'cin' is not a member of 'std'
    5 |   string s; std::cin >> s;
      |                  ^~~
a.cc:3:1: note: 'std::cin' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
    2 | #include<string>
  +++ |+#include <iostream>
    3 | 
a.cc:5:25: error: 's' was not declared in this scope
    5 |   string s; std::cin >> s;
      |                         ^
a.cc:7:10: error: 'cout' is not a member of 'std'
    7 |     std::cout << s[i];
      |          ^~~~
a.cc:7:10: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:9:8: error: 'cout' is not a member of 'std'
    9 |   std::cout << std::endl;
      |        ^~~~
a.cc:9:8: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:9:21: error: 'endl' is not a member of 'std'
    9 |   std::cout << std::endl;
      |                     ^~~~
a.cc:3:1: note: 'std::endl' is defined in header '<ostream>'; this is probably fixable by adding '#include <ostream>'
    2 | #include<string>
  +++ |+#include <ostream>
    3 |
Language: C++

#include <bits/stdc++.h>
using namespace std;

int main(){

string s,t;
  cin >> s;
  
  for(int i=;i<s.size();i++){
   if(i%2==0)t+=s[i];

}
  cout << t << endl;
  
}

Compiler output:
a.cc: In function 'int main()':
a.cc:9:13: error: expected primary-expression before ';' token
    9 |   for(int i=;i<s.size();i++){
      |             ^
Language: C++

#include <bits/stdc++.h>
using namespace std;

int main(){
  string s;
  cin >> s;
  
  string new="";
  for(int i=0; i < s.size(); i+=2){
    new = new + s.at(i);
  }
  cout << new << endl;
  
}

Compiler output:
a.cc: In function 'int main()':
a.cc:8:10: error: expected unqualified-id before 'new'
    8 |   string new="";
      |          ^~~
a.cc:10:9: error: expected type-specifier before '=' token
   10 |     new = new + s.at(i);
      |         ^
a.cc:10:15: error: expected type-specifier before '+' token
   10 |     new = new + s.at(i);
      |               ^
a.cc:12:15: error: expected type-specifier before '<<' token
   12 |   cout << new << endl;
      |               ^~
Language: C++

#include <bits/stdc++.h>
using namespace std;
using ll =long long;
#define all(v) v.begin(),v.end()
 
int main() {
  string S;
  cin>>S;
  for(ll i=0;i<N;i+=2) {
      cout<<S[i];
  }
  cout<<endl;
  
  }

Compiler output:
a.cc: In function 'int main()':
a.cc:9:16: error: 'N' was not declared in this scope
    9 |   for(ll i=0;i<N;i+=2) {
      |                ^
Language: C++

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
#define INF 1e12

#define PB push_back
#define PF push_front
#define fi first
#define se second
#define pii pair<int, int>
#define pll pair<ll, ll>
#define vi vector<int>
#define vpi vector<pii>
#define vll vector<ll>
#define vpl vector<pll>
#define vvi vector<vector<int>>
#define vvl vector<vector<ll>>
#define MX(x) *max_element(all(x))
#define MN(x) *min_element(all(x))
#define ios ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0)
#define pr_d(x) cout << fixed << setprecision(15) << x << endl
#define ud(c, x) distance(c.begin(), upper_bound(all(c), x))
#define ld(c, x) distance(c.begin(), lower_bound(all(c), x))
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i, a, b) for (int i = (a); i < (b); ++i)
#define rep3(i, n) for (int i = (n - 1); i >= 0; --i)
#define rep4(i, a, b) for (int i = (a); i > (b); --i)
#define pb push_back
#define out(x) cout << x << "\n"
bool odd(int i) { return i % 2; }

#define all(v) v.begin(), v.end()
#define size(x) int(x.size())

int gcd(int a, int b) { return __gcd(a, b); }
int lcm(int a, int b) { return a * (b / gcd(a, b)); }
void Yes_No(bool f) {
  if (f)
    printf("Yes\n");
  else
    printf("No\n");
}
void YES_NO(bool f) {
  if (f)
    printf("YES\n");
  else
    printf("NO\n");
}

template <typename T>
void deb1(T x) {
  cout << x << "\n";
}

template <typename T>
bool chmax(T& a, const T& b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T>
bool chmin(T& a, const T& b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
//-------------------ここから回答する-----------------------

void solve(void) {
  string s;
  cin >> s;
  rep(i, size(s)) if (odd(i + 1)) cout(s[i]);
  cout << endl;
}
int main(void) { solve(); }

Compiler output:
a.cc: In function 'void solve()':
a.cc:77:39: error: no match for call to '(std::ostream {aka std::basic_ostream<char>}) (__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type&)'
   77 |   rep(i, size(s)) if (odd(i + 1)) cout(s[i]);
      |                                   ~~~~^~~~~~
Language: C++

#include <iostream>
using namespace std;

int main(){
  string s;
  cin >>s;
  
  string l;
  int long = s.size();
  for(int i = 0; i < long; i++){
    if(i % 2 == 1){
      l.at(i / 2 + 1) = s.at(i);
    }
    
  }
  cout << l << endl;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:9:12: error: expected unqualified-id before '=' token
    9 |   int long = s.size();
      |            ^
a.cc:10:22: error: expected primary-expression before 'long'
   10 |   for(int i = 0; i < long; i++){
      |                      ^~~~
a.cc:10:21: error: expected ';' before 'long'
   10 |   for(int i = 0; i < long; i++){
      |                     ^~~~~
      |                     ;
a.cc:10:22: error: expected primary-expression before 'long'
   10 |   for(int i = 0; i < long; i++){
      |                      ^~~~
a.cc:10:21: error: expected ')' before 'long'
   10 |   for(int i = 0; i < long; i++){
      |      ~              ^~~~~
      |                     )
a.cc:10:22: error: declaration does not declare anything [-fpermissive]
   10 |   for(int i = 0; i < long; i++){
      |                      ^~~~
a.cc:10:28: error: 'i' was not declared in this scope
   10 |   for(int i = 0; i < long; i++){
      |                            ^
Language: C++

#include <isotream>
using namespace std;

int main(){
  string s;
  cin >>s;
  
  string l;
  for(int i = 0; i < s.size(); i++){
    if(i % 2 == 1){
      l.at(i / 2 + 1) = s.at(i);
    }
    
  }
  cout << l << endl;
}

Compiler output:
a.cc:1:10: fatal error: isotream: No such file or directory
    1 | #include <isotream>
      |          ^~~~~~~~~~
compilation terminated.
Language: C++

#include<bits/stdc++.h>
using namesapce std;

int main(){
 string S;
  cin >> S;
  string ans;
  for(int i=0; i<S.size(); i+=2){
   ans += S[i]; 
  }
  cout << ans << "\n";
}


Compiler output:
a.cc:2:7: error: expected nested-name-specifier before 'namesapce'
    2 | using namesapce std;
      |       ^~~~~~~~~
a.cc: In function 'int main()':
a.cc:5:2: error: 'string' was not declared in this scope
    5 |  string S;
      |  ^~~~~~
a.cc:5:2: note: suggested alternatives:
In file included from /usr/include/c++/14/string:41,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52,
                 from a.cc:1:
/usr/include/c++/14/bits/stringfwd.h:77:33: note:   'std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
/usr/include/c++/14/string:76:11: note:   'std::pmr::string'
   76 |     using string    = basic_string<char>;
      |           ^~~~~~
a.cc:6:3: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    6 |   cin >> S;
      |   ^~~
      |   std::cin
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:146:
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:6:10: error: 'S' was not declared in this scope
    6 |   cin >> S;
      |          ^
a.cc:7:9: error: expected ';' before 'ans'
    7 |   string ans;
      |         ^~~~
      |         ;
a.cc:9:4: error: 'ans' was not declared in this scope; did you mean 'abs'?
    9 |    ans += S[i];
      |    ^~~
      |    abs
a.cc:11:3: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   11 |   cout << ans << "\n";
      |   ^~~~
      |   std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:11:11: error: 'ans' was not declared in this scope; did you mean 'abs'?
   11 |   cout << ans << "\n";
      |           ^~~
      |           abs
Language: C++

#include<bits/stdc++.h>
using namesapce std;

int main(){
 string S;
  cin >> S;
  string ans;
  for(int i=1; i<S.size(); i+=2){
   ans += S[i]; 
  }
  cout << ans << "\n";
}

Compiler output:
a.cc:2:7: error: expected nested-name-specifier before 'namesapce'
    2 | using namesapce std;
      |       ^~~~~~~~~
a.cc: In function 'int main()':
a.cc:5:2: error: 'string' was not declared in this scope
    5 |  string S;
      |  ^~~~~~
a.cc:5:2: note: suggested alternatives:
In file included from /usr/include/c++/14/string:41,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52,
                 from a.cc:1:
/usr/include/c++/14/bits/stringfwd.h:77:33: note:   'std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
/usr/include/c++/14/string:76:11: note:   'std::pmr::string'
   76 |     using string    = basic_string<char>;
      |           ^~~~~~
a.cc:6:3: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    6 |   cin >> S;
      |   ^~~
      |   std::cin
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:146:
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:6:10: error: 'S' was not declared in this scope
    6 |   cin >> S;
      |          ^
a.cc:7:9: error: expected ';' before 'ans'
    7 |   string ans;
      |         ^~~~
      |         ;
a.cc:9:4: error: 'ans' was not declared in this scope; did you mean 'abs'?
    9 |    ans += S[i];
      |    ^~~
      |    abs
a.cc:11:3: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   11 |   cout << ans << "\n";
      |   ^~~~
      |   std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:11:11: error: 'ans' was not declared in this scope; did you mean 'abs'?
   11 |   cout << ans << "\n";
      |           ^~~
      |           abs
Language: Java

import java.util.*;
public class Main{
  	public static void main (String [] args){
      	Scanner scanner = new Scanner (System.in);
        String in = scanner.next();
     	String out = "";
      	for (int i = 0; i < in.length; i+=2){
          	out = out + in.charAt(i);
        }
      	System.out.println(out);
    }
}

Compiler output:
Main.java:7: error: cannot find symbol
      	for (int i = 0; i < in.length; i+=2){
      	                      ^
  symbol:   variable length
  location: variable in of type String
1 error
Language: Java

import java.util.*;
public class Main{
  	public static void main (String [] args){
      	Scanner scanner = new Scanner (System.in);
        String in = scanner.next();
     	String out = "";
      	for (int i = 0; i < in.length; i+2){
          	out = out + in.charAt(i);
        }
      	System.out.println(out);
    }
}

Compiler output:
Main.java:7: error: not a statement
      	for (int i = 0; i < in.length; i+2){
      	                                ^
1 error
Language: C++

#include <bits/stdc++.h>
using namespace std;

int main() {
  string S;
  cin >> S;
  for (int i = 0; i < N; i++) {
    if (i % 2) cout << S.at(i);
  }
  cout << "\n";
}

Compiler output:
a.cc: In function 'int main()':
a.cc:7:23: error: 'N' was not declared in this scope
    7 |   for (int i = 0; i < N; i++) {
      |                       ^
Language: C++

#include<bits/stdc++.h>

int main(){
  string s;
  cin >> s;
  
  for(int i=0; i<s.size(); i++){
    if(i%2==0) cout << s[i];
  }
}


Compiler output:
a.cc: In function 'int main()':
a.cc:4:3: error: 'string' was not declared in this scope
    4 |   string s;
      |   ^~~~~~
a.cc:4:3: note: suggested alternatives:
In file included from /usr/include/c++/14/string:41,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52,
                 from a.cc:1:
/usr/include/c++/14/bits/stringfwd.h:77:33: note:   'std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
/usr/include/c++/14/string:76:11: note:   'std::pmr::string'
   76 |     using string    = basic_string<char>;
      |           ^~~~~~
a.cc:5:3: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    5 |   cin >> s;
      |   ^~~
      |   std::cin
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:146:
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:5:10: error: 's' was not declared in this scope
    5 |   cin >> s;
      |          ^
a.cc:8:16: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    8 |     if(i%2==0) cout << s[i];
      |                ^~~~
      |                std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
Language: C

#include <bits/stdc++.h>
#include <math.h>
using namespace std;
typedef long long ll;
typedef vector<ll> vint;
#define rep(i,n) for (ll i = 0; i < (ll)(n); ++i)
#define rrep(a,b,n) for(ll a = (ll)(b); a < (ll)(n); a++)
#define mrep(i,n) for (ll i = (ll)(n); i > 0; i--)
#define be(v) (v).begin(), (v).end()
#define dcout cout << fixed << setprecision(20) 
ll INF = 1LL << 60;
ll mod = 1e9 + 7;

int main() {
	string s; cin >> s;
	for(int i=0;i<s.size();i+=2) cout << s[i];
	cout << endl;
}

Compiler output:
main.c:1:10: fatal error: bits/stdc++.h: No such file or directory
    1 | #include <bits/stdc++.h>
      |          ^~~~~~~~~~~~~~~
compilation terminated.
Language: C++

#include<bits/stdc++.h>
using namespace std;
int main(){
  string s;
  cin >> s;
  string ans;
  for(int i=0;i<s.size();i++){
    if(i/2)
      break;
    else
      ans+=s.at(i)
    
  }
  cout << ans << endl;
  
}


Compiler output:
a.cc: In function 'int main()':
a.cc:11:19: error: expected ';' before '}' token
   11 |       ans+=s.at(i)
      |                   ^
      |                   ;
   12 | 
   13 |   }
      |   ~
Language: C++

#include<bits/stdc++.h>
using namespace std;
int main(){
  string s;
  cin >> s;
  for(int i=0;i<s.size(),i++){
    if(i%2==0){
      cout << s[i] << endl;
    }else
      continue;
  }
}

Compiler output:
a.cc: In function 'int main()':
a.cc:6:29: error: expected ';' before ')' token
    6 |   for(int i=0;i<s.size(),i++){
      |                             ^
      |                             ;
Language: C++

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, srt, end) for (long long i = (srt); i < (long long)(end); i++)


int main(){
    string s;
    cin>>s;
    string ans;
    ll cnt=0;
    rep(i,0,s.size())[
        if(i%2==1){ans[cnt]=s[i];cnt++;}
    ]
    cout<<ans<<endl;
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:13:9: error: expected identifier before 'if'
   13 |         if(i%2==1){ans[cnt]=s[i];cnt++;}
      |         ^~
a.cc: In lambda function:
a.cc:15:5: error: expected '{' before 'cout'
   15 |     cout<<ans<<endl;
      |     ^~~~
a.cc: In function 'int main()':
a.cc:14:6: error: expected ';' before 'cout'
   14 |     ]
      |      ^
      |      ;
   15 |     cout<<ans<<endl;
      |     ~~~~
Language: C++

#include <bits/stdc++.h>
using namespace std;

int main(){
  string s;
  cin>>s;
  for(int i=0;i<s.size()i+=2)
    cout<<s[i]<<endl;
  cout<<endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:7:25: error: expected ';' before 'i'
    7 |   for(int i=0;i<s.size()i+=2)
      |                         ^
      |                         ;
Language: C++

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll INF = 1e16;
const ll mod = 1000000007;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)

template<class T> inline bool chmax(T& a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template<class T> inline bool chmin(T& a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
int ctoi(char c) {
  if (c >= '0' && c <= '9') {
    return c - '0';
  }
  return 0;
}
ll factorial(ll n) {
  if (n == 1) {
    return 1;
  }
  ll ans = factorial(n-1);
  return ans*n;
}
ll gcd(ll a, ll b) {
  if (b == 0) return a;
  return gcd(b, a%b);
}
ll lcm(ll a, ll b) {
  return (a/gcd(a, b))*b;
}
bool is_prime(ll n) {
  for (ll i = 2; i*i <= n; i++) {
    if (n%i == 0) return false;
  }
  return n != 1;
}
ll mod_pow(ll x, ll n, ll mod) {
  if (n == 0) return 1;
  ll res = mod_pow(x*x%mod, n/2, mod);
  if (n & 1) res = res * x % mod;
  return res;
}

int main() {
  string s;
  cin >> s;
  rep(i, n) {
    if (i%2 == 0) cout << s.at(i);
  }
  cout << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:58:10: error: 'n' was not declared in this scope
   58 |   rep(i, n) {
      |          ^
a.cc:6:45: note: in definition of macro 'rep'
    6 | #define rep(i, n) for (int i = 0; i < (int)(n); i++)
      |                                             ^
Language: C++

# include <bits/stdc++.h>
using namespace std;

int main(){
  string s;
  cin >> s;
  vector <char> A;
  for (int i=0; i<s.length(); i+=2){
    A.push_back(s.at(i));
  }
  for (int i=0; i<A.length();i++){
    cout << A.at(i);
  }
}


Compiler output:
a.cc: In function 'int main()':
a.cc:11:21: error: 'class std::vector<char>' has no member named 'length'
   11 |   for (int i=0; i<A.length();i++){
      |                     ^~~~~~
Language: C++

#include <bits/stdc++.h>
using namespace std;

int main() {
  string s;
  cin s;
  int n = s.size();
  
  string ans;
  for(int i = 0; i < n; i += 2) {
    ans = s[i];
  }
  
  cout << ans << endl;
}  

Compiler output:
a.cc: In function 'int main()':
a.cc:6:6: error: expected ';' before 's'
    6 |   cin s;
      |      ^~
      |      ;
Language: C++

#include <bits/stdc++.h>
using namespace std;

int main() {
  string s;
  cin >> s;
  
  for(int i = 0; i < (s.size() / 2); i++) {
    s -= s[2 * - 1];
  }
  
  cout << s << endl;
}  


Compiler output:
a.cc: In function 'int main()':
a.cc:9:7: error: no match for 'operator-=' (operand types are 'std::string' {aka 'std::__cxx11::basic_string<char>'} and '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'})
    9 |     s -= s[2 * - 1];
Language: C++

#include <bits/stdc++.h>
using namespace std;

int main() {
  string s;
  for(int i = 0; i < (s.size() / 2); i++) {
    s -= s[2 * i - 1];
  }
  cout << s << endl;
}  

Compiler output:
a.cc: In function 'int main()':
a.cc:7:7: error: no match for 'operator-=' (operand types are 'std::string' {aka 'std::__cxx11::basic_string<char>'} and '__gnu_cxx::__alloc_traits<std::allocator<char>, char>::value_type' {aka 'char'})
    7 |     s -= s[2 * i - 1];
Language: C++

#include <bits/stdc++.h>
using namespace std;

void solve(std::string s) {
string rick;
  for(int i = 1;i<=s.ize();i++){
    if(i%2)rick+=s[i-1];
  }
  cout<<rick;
}

// Generated by 1.1.6 https://github.com/kyuridenamida/atcoder-tools  (tips: You
// use the default template now. You can remove this line by using your custom
// template)
int main() {
  std::string s;
  std::cin >> s;
  solve(s);
  return 0;
}


Compiler output:
a.cc: In function 'void solve(std::string)':
a.cc:6:22: error: 'std::string' {aka 'class std::__cxx11::basic_string<char>'} has no member named 'ize'; did you mean 'size'?
    6 |   for(int i = 1;i<=s.ize();i++){
      |                      ^~~
      |                      size
Language: C++

#include <bits/stdc++.h>
using namespace std;

int main() {
    string s;
    cin >> s;
    for(int i = 0; i < N; i+=2) {
        cout << s[i];
    }
    cout << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:7:24: error: 'N' was not declared in this scope
    7 |     for(int i = 0; i < N; i+=2) {
      |                        ^
Language: C++

#include<iostream>
#include<cmath>
using namespace std;


int main()
{
    string s, s_;
    cin >> s;
    for (int i = 0, int j = 0; i < s.size(); i += 2, j++)
    {
        s_[j] = s[i];
    }
    cout << s_ << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:10:21: error: expected unqualified-id before 'int'
   10 |     for (int i = 0, int j = 0; i < s.size(); i += 2, j++)
      |                     ^~~
a.cc:10:20: error: expected ';' before 'int'
   10 |     for (int i = 0, int j = 0; i < s.size(); i += 2, j++)
      |                    ^~~~
      |                    ;
a.cc:10:44: error: expected ')' before ';' token
   10 |     for (int i = 0, int j = 0; i < s.size(); i += 2, j++)
      |         ~                                  ^
      |                                            )
a.cc:10:46: error: 'i' was not declared in this scope
   10 |     for (int i = 0, int j = 0; i < s.size(); i += 2, j++)
      |                                              ^
a.cc:10:54: error: 'j' was not declared in this scope
   10 |     for (int i = 0, int j = 0; i < s.size(); i += 2, j++)
      |                                                      ^
Language: C++

#include<iostream>
#include<cmath>
using namespace std;


int main()
{
    string s;
  	char s_[100000];
    cin >> s;
    for (int i = 0, int j = 0; i < s.size(); i += 2, j++)
    {
        s_[j] = s[i];
    }
    cout << s_ << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:11:21: error: expected unqualified-id before 'int'
   11 |     for (int i = 0, int j = 0; i < s.size(); i += 2, j++)
      |                     ^~~
a.cc:11:20: error: expected ';' before 'int'
   11 |     for (int i = 0, int j = 0; i < s.size(); i += 2, j++)
      |                    ^~~~
      |                    ;
a.cc:11:44: error: expected ')' before ';' token
   11 |     for (int i = 0, int j = 0; i < s.size(); i += 2, j++)
      |         ~                                  ^
      |                                            )
a.cc:11:46: error: 'i' was not declared in this scope
   11 |     for (int i = 0, int j = 0; i < s.size(); i += 2, j++)
      |                                              ^
a.cc:11:54: error: 'j' was not declared in this scope
   11 |     for (int i = 0, int j = 0; i < s.size(); i += 2, j++)
      |                                                      ^
Language: C

#include<stdio.h>
#inlcude<string.h>
int main(void){
  char s[101];
  scanf("%s",s);
  int len=strlen(s);
  for(int i=0;i<len;i+=2){
    printf("%c",s[i]);
  }
  return 0;
}

Compiler output:
main.c:2:2: error: invalid preprocessing directive #inlcude; did you mean #include?
    2 | #inlcude<string.h>
      |  ^~~~~~~
      |  include
main.c: In function 'main':
main.c:6:11: error: implicit declaration of function 'strlen' [-Wimplicit-function-declaration]
    6 |   int len=strlen(s);
      |           ^~~~~~
main.c:2:1: note: include '<string.h>' or provide a declaration of 'strlen'
    1 | #include<stdio.h>
  +++ |+#include <string.h>
    2 | #inlcude<string.h>
main.c:6:11: warning: incompatible implicit declaration of built-in function 'strlen' [-Wbuiltin-declaration-mismatch]
    6 |   int len=strlen(s);
      |           ^~~~~~
main.c:6:11: note: include '<string.h>' or provide a declaration of 'strlen'
Language: C++

#include<iostream>
#include<string>
int main(){
  string s;
  cin>>s;
  for(int i=0;i<s.size();i=i+2){
    cout<<s[i];
  }
  cout<<endl;
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:4:3: error: 'string' was not declared in this scope
    4 |   string s;
      |   ^~~~~~
a.cc:4:3: note: suggested alternatives:
In file included from /usr/include/c++/14/iosfwd:41,
                 from /usr/include/c++/14/ios:40,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stringfwd.h:77:33: note:   'std::string'
   77 |   typedef basic_string<char>    string;
      |                                 ^~~~~~
In file included from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44:
/usr/include/c++/14/string:76:11: note:   'std::pmr::string'
   76 |     using string    = basic_string<char>;
      |           ^~~~~~
a.cc:5:3: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    5 |   cin>>s;
      |   ^~~
      |   std::cin
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:5:8: error: 's' was not declared in this scope
    5 |   cin>>s;
      |        ^
a.cc:7:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    7 |     cout<<s[i];
      |     ^~~~
      |     std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:9:3: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    9 |   cout<<endl;
      |   ^~~~
      |   std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:9:9: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
    9 |   cout<<endl;
      |         ^~~~
      |         std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
Language: C++

#include <iostream>
#include <string>
using namespace std;

int main()
{
    string s;
    cin >> s;
    for (int i=0; i<s.size; i+=2) cout << s[i];
    cout << '\n';

    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:9:23: error: invalid use of member function 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size_type std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size() const [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; size_type = long unsigned int]' (did you forget the '()' ?)
    9 |     for (int i=0; i<s.size; i+=2) cout << s[i];
      |                     ~~^~~~
      |                           ()
Language: C++

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)

 
int main() {
    string s;
    cin>>s;

    strng ans;
    for(int i=0;i<s.length();i+=2)ans+=s[i];
    cout<<ans<<endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:11:5: error: 'strng' was not declared in this scope
   11 |     strng ans;
      |     ^~~~~
a.cc:12:35: error: 'ans' was not declared in this scope; did you mean 'abs'?
   12 |     for(int i=0;i<s.length();i+=2)ans+=s[i];
      |                                   ^~~
      |                                   abs
a.cc:13:11: error: 'ans' was not declared in this scope; did you mean 'abs'?
   13 |     cout<<ans<<endl;
      |           ^~~
      |           abs
Language: C++

#include <iostream>
#include <vector>
#include <cmath>
using namespace std;
int main() {
  string S;
  cin>>S;
  for (int i=0; i<S.size(); i=i+2){
  cout<<s.at(i);}}

Compiler output:
a.cc: In function 'int main()':
a.cc:9:9: error: 's' was not declared in this scope
    9 |   cout<<s.at(i);}}
      |         ^
Language: C++

#include <iostream>
#include <string>
using namespace std;

int main(){
    string s,t;
    cin >> s;
    int N = (int)(s.length());
    for (int i=0; i < N; ++i){
        if (i % 2 == 0){
            t[i/2] = s[i];
        }
    cout << t << endl;
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:15:2: error: expected '}' at end of input
   15 | }
      |  ^
a.cc:5:11: note: to match this '{'
    5 | int main(){
      |           ^
Language: C++

#include <iostream>
#include <string>
using namespace std;

int main(){
    string s,t;
    cin >> s;
    for (int i=0; i < N; ++i){
        if (i % 2 == 0){
            t[i/2] = s[i];
        }
    cout << t << endl;
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:8:23: error: 'N' was not declared in this scope
    8 |     for (int i=0; i < N; ++i){
      |                       ^
a.cc:14:2: error: expected '}' at end of input
   14 | }
      |  ^
a.cc:5:11: note: to match this '{'
    5 | int main(){
      |           ^
Language: C++

#include <iostream>
#include <string>
using namespace std;

int main(){
    string s,t;
    cin >> s;
    for (int i=0; i < N; ++i){
        if (i % 2 == 0){
            t[i/2] = s[i]
        }
    cout << t << endl;
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:8:23: error: 'N' was not declared in this scope
    8 |     for (int i=0; i < N; ++i){
      |                       ^
a.cc:10:26: error: expected ';' before '}' token
   10 |             t[i/2] = s[i]
      |                          ^
      |                          ;
   11 |         }
      |         ~                 
a.cc:14:2: error: expected '}' at end of input
   14 | }
      |  ^
a.cc:5:11: note: to match this '{'
    5 | int main(){
      |           ^
Language: C

#include<stdio.h>
#include<string.h>
int main(void){
  char *s;
  scanf("%s",s);
  int len_s=strlen(s);
  for(int loop=0;loop<len;loop++){
    if(loop%2!=0){
      printf("%c",s[loop]);
    }
  }
  putchar('\n');
  return 0;
}

Compiler output:
main.c: In function 'main':
main.c:7:23: error: 'len' undeclared (first use in this function); did you mean 'len_s'?
    7 |   for(int loop=0;loop<len;loop++){
      |                       ^~~
      |                       len_s
main.c:7:23: note: each undeclared identifier is reported only once for each function it appears in
Language: C

#include <stdio.h>
#include <string.h>
 
int main(void)
{
    int n,i;   
    char s[100];
      
    n=strlen(s);
    for(i=0;i<n;i++){
       if(i%2==0) printf("%d",s[i]);
    }
    printf("\n");
  
    return 0;

Compiler output:
main.c: In function 'main':
main.c:15:5: error: expected declaration or statement at end of input
   15 |     return 0;
      |     ^~~~~~
Language: C

#include <stdio.h>
#include <string.h>
 
int main(void)
{
    int n,i;   
    char s[100];
      
    n=strlen(s);
    for(i=1;in-1;i++){
       if(i%2!=0) printf("%d",s[i]);
    }
    printf("\n");
  
    return 0;
}

Compiler output:
main.c: In function 'main':
main.c:10:13: error: 'in' undeclared (first use in this function); did you mean 'i'?
   10 |     for(i=1;in-1;i++){
      |             ^~
      |             i
main.c:10:13: note: each undeclared identifier is reported only once for each function it appears in
Language: C

#include <stdio.h>

int main(void)
{
    int n;   
    char s
      
    n=strlen(s);
    for(i=0;i<n;i++){
       if(i%2==0) printf("%d",s[i]);
    }
    printf("\n");
  
    return 0;
}


Compiler output:
main.c: In function 'main':
main.c:8:5: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'n'
    8 |     n=strlen(s);
      |     ^
main.c:8:7: error: implicit declaration of function 'strlen' [-Wimplicit-function-declaration]
    8 |     n=strlen(s);
      |       ^~~~~~
main.c:2:1: note: include '<string.h>' or provide a declaration of 'strlen'
    1 | #include <stdio.h>
  +++ |+#include <string.h>
    2 | 
main.c:8:7: warning: incompatible implicit declaration of built-in function 'strlen' [-Wbuiltin-declaration-mismatch]
    8 |     n=strlen(s);
      |       ^~~~~~
main.c:8:7: note: include '<string.h>' or provide a declaration of 'strlen'
main.c:8:14: error: 's' undeclared (first use in this function)
    8 |     n=strlen(s);
      |              ^
main.c:8:14: note: each undeclared identifier is reported only once for each function it appears in
main.c:9:9: error: 'i' undeclared (first use in this function)
    9 |     for(i=0;i<n;i++){
      |         ^
Language: C++

#include <iostream>
using namespace std;

int main() {
  string s;
  cin >> s;
  int a = s.size();
  for(i=1 i<a i+2){
    cout << s[i];
  }
  cout << endl;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:8:7: error: 'i' was not declared in this scope
    8 |   for(i=1 i<a i+2){
      |       ^
a.cc:12:1: error: expected primary-expression before '}' token
   12 | }
      | ^
a.cc:11:16: error: expected ')' before '}' token
   11 |   cout << endl;
      |                ^
      |                )
   12 | }
      | ~               
a.cc:8:6: note: to match this '('
    8 |   for(i=1 i<a i+2){
      |      ^
a.cc:12:1: error: expected primary-expression before '}' token
   12 | }
      | ^
Language: C++

#include <iostream>
using namespace std;

int main() {
  string s;
  cin >> s:
  int a = s.size();
  for(i=1 i<a i+2){
    cout << s[i];
  }
  cout << endl;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:6:11: error: expected ';' before ':' token
    6 |   cin >> s:
      |           ^
      |           ;
a.cc:8:7: error: 'i' was not declared in this scope
    8 |   for(i=1 i<a i+2){
      |       ^
a.cc:12:1: error: expected primary-expression before '}' token
   12 | }
      | ^
a.cc:11:16: error: expected ')' before '}' token
   11 |   cout << endl;
      |                ^
      |                )
   12 | }
      | ~               
a.cc:8:6: note: to match this '('
    8 |   for(i=1 i<a i+2){
      |      ^
a.cc:12:1: error: expected primary-expression before '}' token
   12 | }
      | ^
Language: C++

#include <iostream>
using namespace std;

int main(){
  string s;
  int i;
  cin>>s;
  string t;
  
  for(i=0;i<s.size();i=2*i){
    t=s[i]
  }
  cout<<t<<endl;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:11:11: error: expected ';' before '}' token
   11 |     t=s[i]
      |           ^
      |           ;
   12 |   }
      |   ~
Language: C++

#include<bits/stdc++.h>
using namespace std;
int main(){
	string s;
  vector<int> vec;
  for(int i=0;i<vec.size();i+=2){
	s+=vec.at(i)}
  cout<<s<<endl;

}

Compiler output:
a.cc: In function 'int main()':
a.cc:7:21: error: expected ';' before '}' token
    7 |         s+=vec.at(i)}
      |                     ^
      |                     ;
Language: C++

#include<bits/stdc++.h>
using namespace std;
int main(){
	string s;
  vector<int> vec;
  for(int i=0;i<vec.size;i+=2){
	s+=vec.at(i)}
  cout<<s<<endl;

}

Compiler output:
a.cc: In function 'int main()':
a.cc:6:21: error: invalid use of member function 'std::vector<_Tp, _Alloc>::size_type std::vector<_Tp, _Alloc>::size() const [with _Tp = int; _Alloc = std::allocator<int>; size_type = long unsigned int]' (did you forget the '()' ?)
    6 |   for(int i=0;i<vec.size;i+=2){
      |                 ~~~~^~~~
      |                         ()
a.cc:7:21: error: expected ';' before '}' token
    7 |         s+=vec.at(i)}
      |                     ^
      |                     ;
Language: C++

#include <bits.stdc++.h>
using namespace std;

int main()
{
  string S;
  cin >> S;
  
  for (int i = 0; i < (S.size()+1) / 2;i++) {
    cout << S.at(2 * i);
  }
  cout << endl;
}

Compiler output:
a.cc:1:10: fatal error: bits.stdc++.h: No such file or directory
    1 | #include <bits.stdc++.h>
      |          ^~~~~~~~~~~~~~~
compilation terminated.
Language: C++

#include <bits/stdc++.h>
using namespace std;
int main(){
  string s;
  cin >> s;
  int l = s.length();
  vector<int> a;
  for(int i = 0; i < l; i++){
    (i % 2 == 0) ? a.emplace_back(s[i]) : ;
  } 
}


Compiler output:
a.cc: In function 'int main()':
a.cc:9:43: error: expected primary-expression before ';' token
    9 |     (i % 2 == 0) ? a.emplace_back(s[i]) : ;
      |                                           ^
Language: C++

#include <bits/stdc++.h>
using namespace std;
int main(){
  string s;
  cin >> s;
  int l = s.length();
  vector<int> a;
  for(int i = 0; i < l; i++){
    (i % 2 == 0) ? a.add(c[i]) : ;
  } 
}

Compiler output:
a.cc: In function 'int main()':
a.cc:9:22: error: 'class std::vector<int>' has no member named 'add'
    9 |     (i % 2 == 0) ? a.add(c[i]) : ;
      |                      ^~~
a.cc:9:26: error: 'c' was not declared in this scope
    9 |     (i % 2 == 0) ? a.add(c[i]) : ;
      |                          ^
a.cc:9:34: error: expected primary-expression before ';' token
    9 |     (i % 2 == 0) ? a.add(c[i]) : ;
      |                                  ^
Language: C++

include<bits/stdc++.h>
using namespace std;

int main(){
  string s;
  cin>>s;
  
  for(int i = 0; 2*i+1 < s.length()  ; i++)
    cout<<s[2*i+1]<<endl;
  
}

Compiler output:
a.cc:1:1: error: 'include' does not name a type
    1 | include<bits/stdc++.h>
      | ^~~~~~~
a.cc: In function 'int main()':
a.cc:5:3: error: 'string' was not declared in this scope
    5 |   string s;
      |   ^~~~~~
a.cc:6:3: error: 'cin' was not declared in this scope
    6 |   cin>>s;
      |   ^~~
a.cc:6:8: error: 's' was not declared in this scope
    6 |   cin>>s;
      |        ^
a.cc:9:5: error: 'cout' was not declared in this scope
    9 |     cout<<s[2*i+1]<<endl;
      |     ^~~~
a.cc:9:21: error: 'endl' was not declared in this scope
    9 |     cout<<s[2*i+1]<<endl;
      |                     ^~~~
Language: C++

#include <bits/stdc++.h>
using namespace std;

int main() {
  string s;
  cin>>s;
  int N = s.size();
  string ans;
  for (int i=0, i<N, i+=2) ans += s[i];
  cout << ans << endl;
  
  
  
  
}


Compiler output:
a.cc: In function 'int main()':
a.cc:9:18: error: expected ';' before '<' token
    9 |   for (int i=0, i<N, i+=2) ans += s[i];
      |                  ^
      |                  ;
a.cc:9:18: error: expected primary-expression before '<' token
a.cc:9:26: error: expected ';' before ')' token
    9 |   for (int i=0, i<N, i+=2) ans += s[i];
      |                          ^
      |                          ;
Language: C++

#include <bits/stdc++.h>
using namespace std;
 
int main() {
string s;
  cin >> s;
  int i = 0; // カウンタ変数
while (i < s.size()) {
   cout << s.at(i)
  i += 2;
}
  cout << endl;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:9:19: error: expected ';' before 'i'
    9 |    cout << s.at(i)
      |                   ^
      |                   ;
   10 |   i += 2;
      |   ~
Language: C++

#include <iostream>
#include <sitrng>

using namespace std;

string even (string s )
{
  string ans;

  for ( int i = 0; i < s.size(); i += 2 ) ans += s[i];

  return ans;
}

int main()
{
  string s;

  cin >> s;

  cout << even(s) << "\n";
}


Compiler output:
a.cc:2:10: fatal error: sitrng: No such file or directory
    2 | #include <sitrng>
      |          ^~~~~~~~
compilation terminated.
Language: C++

#include <bits/stdc++.h>
using namespace std;

#ifdef LOCAL
#define debug(var) cerr << #var << " = " << var << endl;
#else
#define debug(var)
#endif

void init() {
	ios_base::sync_with_stdio(0);
	cin.tie(0); cout.tie(0);
}

void solve() {
	string s; cin s;
	for (int i = 0; i < s.size(); ++i) {
		if (i%2) continue;
		cout << s[i];
	}
}

int main() {
	init();
	int t = 1; //scanf("%d", &t);
	while (t--) {
		solve();
	}
	return 0;
}


Compiler output:
a.cc: In function 'void solve()':
a.cc:16:22: error: expected ';' before 's'
   16 |         string s; cin s;
      |                      ^~
      |                      ;
Language: C++

#include <bits/stdc++.h>
using namespace std;
int main(){
    string s;cin >> s;
    for(auto i = 0; i < s.size(); i += 2) {
        cout << s[i];
    }
  　cout << endl;
}

Compiler output:
a.cc:8:3: error: extended character 　 is not valid in an identifier
    8 |   　cout << endl;
      |   ^
a.cc: In function 'int main()':
a.cc:8:3: error: '\U00003000cout' was not declared in this scope
    8 |   　cout << endl;
      |   ^~~~~~
Language: C

#include<stdio.h>
#include<string.h>
int main(void){
  char str[100000];
  scanf("%s",str);
  for(int i=0;i<string(str);i+=2){
    printf("%c",str[i]);
  }
  return 0;
}

Compiler output:
main.c: In function 'main':
main.c:6:17: error: implicit declaration of function 'string'; did you mean 'stdin'? [-Wimplicit-function-declaration]
    6 |   for(int i=0;i<string(str);i+=2){
      |                 ^~~~~~
      |                 stdin
Language: C++

#include<iostream>
#include<string>
#include<vector>
#include<math.h>
#include<algorithm>
#include<cstdio>
#include<stdio.h>
#include<stack>
#include<sstream>
#include<iomanip>
#include<map>
#include<unordered_map>
#include<list>
#include<numeric>
typedef long long ll;

#define pi 3.14159265358979323846
#define VI vector<int>
#define VLL vector<long long>
#define MAX max_element
#define MIN min_element
#define all(v) v.begin(), v.end()
const ll MOD = 1e9 + 7;
using namespace std;
template<typename T>
T gcd(T a, T b) {
	return b ? gcd(b, a % b) : a;
}
template<typename T>
T lcm(T a, T b) {
	return a * b / gcd(a, b);
}

template<typename T>
T finder(vector<T> vec, T number) {
	auto itr = find(vec.begin(), vec.end(), number);
	size_t index = distance(vec.begin(), itr);
	if (index != vec.size()) { // 発見できたとき
		return 1;
	}
	else { // 発見できなかったとき
		return 0;
	}
}
ll frac(ll n)
{
	if (n == 0) {
		return 1;
	}
	return (n * frac(n - 1)) % MOD;
}

/*char r[4];
int yaju[4];
char op[3];
int sum = 0;
scanf("%s", r);
for (int i = 0;i < 4;i++) {
	yaju[i] = r[i] - '0';
}
*/
int main() {
	string s; cin >> s;
	for (int i = 0;i < s.size();i+=2) {
		cout << s[i];
	}
}a

Compiler output:
a.cc:67:2: error: 'a' does not name a type
   67 | }a
      |  ^
Language: C++

#include <bits/stdc++.h>
using namespace std;
int main(){
  string s;
  cin >> s;
  int n = s.size();
  string ans;
  for(int i=0;i<n;i+=2){
    ans += s[i]
  }
  cout << ans << endl;
  return 0;
}



Compiler output:
a.cc: In function 'int main()':
a.cc:9:16: error: expected ';' before '}' token
    9 |     ans += s[i]
      |                ^
      |                ;
   10 |   }
      |   ~