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

#include <stdio.h>
#include <map>
#include <algorithm>
#include <vector>
#include <queue>

#define INF 1 << 29
#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define FOR(i,k,n) for(int i=(k);i<(int)(n);i++)

using namespace std;

typedef pair<int,int> s;
typedef long long int ll;

int abs(int x){
  return x > 0 ? x : -x;
}

int length(char c[]){
  int cnt=0;
  for(cnt=0;c[cnt]!='\0';cnt++){
  }
  return cnt;
}
char S[1000000];
int a[27];

int main(){
  scanf("%s",S);
  for(int i=0;S[i]!='\0'){
    a[S[i]-'a']++;
  }
  REP(i,26){
    if(a[i]==0){
      printf("c\n",'a'+i);
      return 0;
    }
  }
  printf("None\n");
  return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:31:25: error: expected ';' before ')' token
   31 |   for(int i=0;S[i]!='\0'){
      |                         ^
      |                         ;
Language: C

#include <stdio.h>
int main(void)
{
  char s[100002],p,c;
  char a[256]={0};
  scanf("%s",s);
  for(p=s;*p!='\0';++p){
    a[*p]=1;
  }
  for(c='a';c<='z';++c){
    if(a[c]==0) break;
  }
  if(c>'z')
    printf("None\n");
  else
    printf("%c\n", c);
  return 0;
}


Compiler output:
main.c: In function 'main':
main.c:7:8: error: assignment to 'char' from 'char *' makes integer from pointer without a cast [-Wint-conversion]
    7 |   for(p=s;*p!='\0';++p){
      |        ^
main.c:7:11: error: invalid type argument of unary '*' (have 'int')
    7 |   for(p=s;*p!='\0';++p){
      |           ^~
main.c:8:7: error: invalid type argument of unary '*' (have 'int')
    8 |     a[*p]=1;
      |       ^~
Language: C++

#include <iostream>
#include <vector>
using namespace std;
 
int main(){
	string S;
	cin >> S;
	vector<char> alphabets{'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'v', 'w', 'z'};
	for(int i = 0; i < S.size(); i++){
		for(int j = 0; j < alphabets.size(); j++){
			if(S[i] == alphabets[j]){
				alphabets.erase(alphabets.begin() + j);
			}
		}
	}
	if(alphabets.size()){
		cout << "None" << endl;
	}else{
		cout << alphabets[i] << endl;
	}
}

Compiler output:
a.cc: In function 'int main()':
a.cc:19:35: error: 'i' was not declared in this scope
   19 |                 cout << alphabets[i] << endl;
      |                                   ^
Language: C++

//abc071_b Not Found


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

namespace
{
bool bFlag[ 30 ];
}

int main()
{
int i;
char S[ 100010 ];
char C;

	cin >> S;

	i = 0;
	C = S[ i ];
	while( C != '\0' )
	{
		bFlag[ C - 'a' ] = true;

		i++;
		C = S[ i ];
	}

	for( i = 0; i < 26; i++ )
	{
		if( ! bFlag[ i ] ) break;
	}

	if( i >= 26 )
		cout << "None" << endl;]
	else
		cout << (char) ( 'a' + i ) << endl;

	return 0;
}






Compiler output:
a.cc: In function 'int main()':
a.cc:36:40: error: expected primary-expression before ']' token
   36 |                 cout << "None" << endl;]
      |                                        ^
Language: C++

#include<iostream>
using namespace std;

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

    char c;
    for (c = 'a'; c <= 'z'; c++) {
      if (s.find(c) != std::string::npos) {
        cout << c << endl;
        break;
      }
    }
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:11:13: error: request for member 'find' in 's', which is of non-class type 'int'
   11 |       if (s.find(c) != std::string::npos) {
      |             ^~~~
Language: C++

#include <iostream>
#include <vector>

using namespace std;

int main(){


  char alf[26]={'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
  char str[100000];
  char c, *p;
  cin >> str;

  for(int i=25; i>=0; i--){
    p = strchr(str,alf[i]);
      //cout << alf[i] << endl;
    if(p == NULL){
      c = *(alf+i);
  //  cout << "c="<< c << endl;
    }
  }

  if(c=='\0'){
    cout << "None" << endl;
  }else{
    cout << c << endl;
  }

}


Compiler output:
a.cc: In function 'int main()':
a.cc:15:9: error: 'strchr' was not declared in this scope
   15 |     p = strchr(str,alf[i]);
      |         ^~~~~~
a.cc:3:1: note: 'strchr' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
    2 | #include <vector>
  +++ |+#include <cstring>
    3 |
Language: C++

int main()
{
	bool flag[27];
	string alphabe = "abcdefghijklmnopqrstuvwxyz";
	string s;
	for (int i = 0; i < 27; i++)
	{
		flag[i] = false;
	}


	cin >> s;

	for (int i = 0; i < s.length(); i++)
	{
		flag[s[i] - 97] = true;
	}

	for (int i = 0; i < 27 ; i++)
	{
		if (!flag[i])
		{
			cout << alphabe[i] << endl;
			break;
		}
		if (i == 26)
		{
			cout << "None" << endl;
		}
	}

	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:4:9: error: 'string' was not declared in this scope
    4 |         string alphabe = "abcdefghijklmnopqrstuvwxyz";
      |         ^~~~~~
a.cc:5:15: error: expected ';' before 's'
    5 |         string s;
      |               ^~
      |               ;
a.cc:12:9: error: 'cin' was not declared in this scope
   12 |         cin >> s;
      |         ^~~
a.cc:12:16: error: 's' was not declared in this scope
   12 |         cin >> s;
      |                ^
a.cc:23:25: error: 'cout' was not declared in this scope
   23 |                         cout << alphabe[i] << endl;
      |                         ^~~~
a.cc:23:33: error: 'alphabe' was not declared in this scope
   23 |                         cout << alphabe[i] << endl;
      |                                 ^~~~~~~
a.cc:23:47: error: 'endl' was not declared in this scope
   23 |                         cout << alphabe[i] << endl;
      |                                               ^~~~
a.cc:28:25: error: 'cout' was not declared in this scope
   28 |                         cout << "None" << endl;
      |                         ^~~~
a.cc:28:43: error: 'endl' was not declared in this scope
   28 |                         cout << "None" << endl;
      |                                           ^~~~
Language: C++

#include<stdio.h>
#include<string.h>
int main(void)
{
	char x[26]="abcdefghijklmnopqrstuvwxyz",s[100001];
	int y[25],i,k,a;
	for(i-0;i<26;i++)  y[i]=0;
	scanf("%s",s);
	a=strlen(s);
	for(i=0;i<a;i++){
		for(k=0;k<26;k++){
			if(s[i]==x[k]){
				y[k]++;
				break;
			}
		}
	}
	a=1;
	for(i=0;i<26;i++){
		if(y[i]==0){
			a=0;
			break;
		}
	}
	if(a==1)  printf("None\n");
	if(a==0)  printf("%c\n",x[i]);
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:5:20: error: initializer-string for 'char [26]' is too long [-fpermissive]
    5 |         char x[26]="abcdefghijklmnopqrstuvwxyz",s[100001];
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
Language: C++

#include<stdio.h>
#include<string.h>
int main(void)
{
	char x[26]="abcdefghijklmnopqrstuvwxyz",s[100001];
	int y[26],i,k,a;
	for(i-0;i<26;i++)  y[i]=0;
	scanf("%s",s);
	a=strlen(s);
	for(i=0;i<a;i++){
		for(k=0;k<26;k++){
			if(s[i]==x[k]){
				y[k]++;
				break;
			}
		}
	}
	a=1;
	for(i=0;i<26;i++){
		if(y[i]==0){
			a=0;
			break;
		}
	}
	if(a==1)  printf("None\n");
	if(a==0)  printf("%c\n",x[i]);
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:5:20: error: initializer-string for 'char [26]' is too long [-fpermissive]
    5 |         char x[26]="abcdefghijklmnopqrstuvwxyz",s[100001];
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
Language: C++

#include <bits/stdc++.h>
using namespace std;
bool vis[27];
char str[100010];

int main(void) {
    while(gets(str)) {
        memset(vis, 0, sizeof(vis));
        for(int i = 0; str[i]; ++i) {
            int idx = str[i] - 'a';
            if(!vis[idx]) vis[idx] = true;
        }
        bool flag = 0;
        for(int i = 0; i < 26; ++i) {
            if(!vis[i]) {
                putchar(i + 'a');
                puts("");
                flag = true;
                break;
            }
        }
        if(!flag) puts("None");
    }
}


Compiler output:
a.cc: In function 'int main()':
a.cc:7:11: error: 'gets' was not declared in this scope; did you mean 'getw'?
    7 |     while(gets(str)) {
      |           ^~~~
      |           getw
Language: Java

import java.util.Scanner;

/**
 * Created by Admin on 2017-08-13.
 */

public class Bit {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        char[] tablice = input.next().toCharArray();
        boolean[] tablica = new boolean[26];
        for (int i = 0; i < tablica.length; i++) {
            char x = tablice[i];
            tablica[x - 'a'] = true;
        }

        for (int i = 0; i < 26; i++) {
            if (tablica[i] == false) {
                System.out.println((char) (i + 'a'));
                return;

            }

        }
    }
}






Compiler output:
Main.java:7: error: class Bit is public, should be declared in a file named Bit.java
public class Bit {
       ^
1 error
Language: C++

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

typedef long long ll;
typedef unsigned long long ull;
typedef unsigned __int128 HASH;
typedef pair<int,int> pii;
typedef pair<ll, ll> pll;
typedef pair<ull, ull> pullull;
typedef pair<ll,int> plli;
typedef pair<double, int> pdbi;
typedef pair<int,pii> pipii;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<pii> vpii;

#define rep(i,n) for (int i=0;i<(n);i++)
#define rep2(i,a,b) for (int i=(a);i<(b);i++)
#define rrep(i,n) for (int i=(n);i>0;i--)
#define rrep2(i,a,b) for (int i=(a);i>b;i--)
#define pb push_back
#define fi first
#define se second
#define all(a) (a).begin(),(a).end()

const ll mod = 1000000000 + 7;
const ll hmod1 = 999999937;
const ll hmod2 = 1000000000 + 9;
const ll INF = 1<<30;
const int dx4[4] = {1, 0, -1, 0};
const int dy4[4] = {0, 1, 0, -1};
const int dx8[8] = {1, 1, 1, 0, 0, -1, -1, -1};
const int dy8[8] = {0, 1, -1, 1, -1, 0, 1, -1};
const double pi = 3.141592653589793;

string s;
int cnt[26];

signed main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    cin >> s;
    rep(i, n) {
        cnt[s[i] - 'a']++;
    }
    rep(i, 26) {
        if (cnt[i] == 0) {
            cout << char(i + 'a') << endl;
            exit(0);
        }
    }
    cout << "None" << endl;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:46:12: error: 'n' was not declared in this scope
   46 |     rep(i, n) {
      |            ^
a.cc:20:34: note: in definition of macro 'rep'
   20 | #define rep(i,n) for (int i=0;i<(n);i++)
      |                                  ^
Language: C++

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

int main(void)
{
    int letters['z' - 'a' + 1];
    string s;

    cin >> s;
    //cout << s << "  xxx" << endl;

    string::size_type sz = s.size();
    //cout << sz << "   number" << endl;
    memset(letters, 0, sizeof(letters));
    for (string::size_type i = 0; i < sz; i++)
    {
        int idx = s.at(i) - 'a';
        //cout << idx << " ";
        letters[idx]++;
    }

    sz = 'z' - 'a' + 1;
    for (int i = 0; i < sz; i++)
    {
        if (letters[i] == 0)
        {
            char out = 'a' + i;
            cout << out << endl;
            return 0;
        }
    }

    cout << "None" << endl;

    return 0;
}



Compiler output:
a.cc: In function 'int main()':
a.cc:16:5: error: 'memset' was not declared in this scope
   16 |     memset(letters, 0, sizeof(letters));
      |     ^~~~~~
a.cc:4:1: note: 'memset' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
    3 | #include <cmath>
  +++ |+#include <cstring>
    4 | using namespace std;
Language: Java

package beginnerContest071;

import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;

public class B {
	public static void main(String[] args) {
		String[] str = new Scanner(System.in).next().split("");
		List<String> each = Arrays.asList(str);
		boolean found = false;

		Collections.sort(each);
		for(char word = 'a'; word <= 'z'; word++) {
			if( !each.contains(String.valueOf(word)) ) {
				System.out.println(word);
				found = true;
				break;
			}
		}
		if( !found ) System.out.println("None");
	}
}


Compiler output:
Main.java:8: error: class B is public, should be declared in a file named B.java
public class B {
       ^
1 error
Language: C++

#include <string>
#include <queue>
#include <stack>
#include <vector>
#include <sstream>
#include <algorithm>
#include <deque>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <list>
#include <cstdio>
#include <iostream>
#include <cmath>
#include <climits>
#include <bitset>
#include <functional>
#include <numeric>
#include <ctime>
#include <cassert>
#include <cstring>
#include <fstream>

#define rep(i, a, b) for(int (i)=(a); (i)<(b); (i)++)
#define irep(i, a, b) for(int (i)=(a);(i)<=(b);(i)++)
#define rrep(i, a, b) for(int (i)=(a);(i)>=(b);(i)--)

using namespace std;

const int MOD = 1e9 + 7;

int main() {
    string s;
    cin >> s;
    bool not[26];
    for (auto c : s)
        not[c - 'a'] = true;
    bool flag = false;
    rep(i, 0, 26) {
        if (!not[i]) {
            flag = true;
            cout << (char)(i + 'a') << endl;
        }
    }
    if (!flag)
        cout << "None" << endl;
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:36:10: error: expected unqualified-id before 'not' token
   36 |     bool not[26];
      |          ^~~
a.cc:38:14: error: expected ',' before '-' token
   38 |         not[c - 'a'] = true;
      |              ^~
      |              ,
a.cc:38:15: error: expected identifier before '-' token
   38 |         not[c - 'a'] = true;
      |               ^
a.cc: In lambda function:
a.cc:38:22: error: expected '{' before '=' token
   38 |         not[c - 'a'] = true;
      |                      ^
a.cc: In function 'int main()':
a.cc:38:9: error: no match for 'operator!' (operand type is 'main()::<lambda()>')
   38 |         not[c - 'a'] = true;
      |         ^~~~~~~~~~~~
a.cc:38:9: note: candidate: 'operator!(bool)' (built-in)
a.cc:38:9: note:   no known conversion for argument 1 from 'main()::<lambda()>' to 'bool'
a.cc: In lambda function:
a.cc:41:20: error: expected '{' before ')' token
   41 |         if (!not[i]) {
      |                    ^
a.cc: In function 'int main()':
a.cc:41:14: error: no match for 'operator!' (operand type is 'main()::<lambda()>')
   41 |         if (!not[i]) {
      |              ^~~~~~
a.cc:41:14: note: candidate: 'operator!(bool)' (built-in)
a.cc:41:14: note:   no known conversion for argument 1 from 'main()::<lambda()>' to 'bool'
Language: C++

#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>
#include<stack>
#include<queue>
#include<vector>
#include<set>
#include<map>
#include<algorithm>
using namespace std;

int main(){
    string s;
    int cnt[26] = {};
    cin >> s;
    for(char c in s){
        cnt[c - 'a']++;
    }
    for(int i = 0;i < 26;i++){
        if(!cnt[i]){
            cout << (char)(i + 'a') << endl;
            return 0;
        }
    }
    cout << "None" << endl;
    return 0;
    
    
    
    
    
    
    
    
}

Compiler output:
a.cc: In function 'int main()':
a.cc:17:15: error: expected ';' before 'in'
   17 |     for(char c in s){
      |               ^~~
      |               ;
a.cc:17:16: error: 'in' was not declared in this scope; did you mean 'yn'?
   17 |     for(char c in s){
      |                ^~
      |                yn
a.cc:17:18: error: expected ';' before 's'
   17 |     for(char c in s){
      |                  ^~
      |                  ;
Language: C++

string s;
	int cnt[26] = {};
	cin >> s;
	for(char c : s){
		cnt[c - 'a']++;
	}
	for(int i = 0;i < 26;i++){
		if(!cnt[i]){
			cout << (char)(i + 'a') << endl;
			return 0;
		}
	}
	cout << "None" << endl;
	return 0;

Compiler output:
a.cc:1:1: error: 'string' does not name a type
    1 | string s;
      | ^~~~~~
a.cc:3:9: error: 'cin' does not name a type
    3 |         cin >> s;
      |         ^~~
a.cc:4:9: error: expected unqualified-id before 'for'
    4 |         for(char c : s){
      |         ^~~
a.cc:7:9: error: expected unqualified-id before 'for'
    7 |         for(int i = 0;i < 26;i++){
      |         ^~~
a.cc:7:23: error: 'i' does not name a type
    7 |         for(int i = 0;i < 26;i++){
      |                       ^
a.cc:7:30: error: 'i' does not name a type
    7 |         for(int i = 0;i < 26;i++){
      |                              ^
a.cc:13:9: error: 'cout' does not name a type
   13 |         cout << "None" << endl;
      |         ^~~~
a.cc:14:9: error: expected unqualified-id before 'return'
   14 |         return 0;
      |         ^~~~~~
Language: C++

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

  bool alp[26];
  for (int i = 0; i < 26; i++) {
    alp[i] = false;
  }
  for (int i = 0; i < S.size(); i++) {
    alp[S[i] - 'a'] = true;
  }
  for (int i = 0; i < 26; i++) {
    if (!alp[i]) {
      cout << (char)(i + 'a') << endl;
      return 0;
    }
  }

  cout << "None" << endl;
  return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:3:3: error: 'string' was not declared in this scope
    3 |   string S;
      |   ^~~~~~
a.cc:4:3: error: 'cin' was not declared in this scope
    4 |   cin >> S;
      |   ^~~
a.cc:4:10: error: 'S' was not declared in this scope
    4 |   cin >> S;
      |          ^
a.cc:15:7: error: 'cout' was not declared in this scope
   15 |       cout << (char)(i + 'a') << endl;
      |       ^~~~
a.cc:15:34: error: 'endl' was not declared in this scope
   15 |       cout << (char)(i + 'a') << endl;
      |                                  ^~~~
a.cc:20:3: error: 'cout' was not declared in this scope
   20 |   cout << "None" << endl;
      |   ^~~~
a.cc:20:21: error: 'endl' was not declared in this scope
   20 |   cout << "None" << endl;
      |                     ^~~~
Language: C++

#include <iostream>
#include <cmath>
using namespace std;
char s [ 10000 + 100 ] ;
int a [ 100 ] ;
int main ( ) {
	memset ( a , 0 , sizeof ( a ) ) ;
	cin >> s ;
	int len = strlen ( s ) ;
	for ( int i = 0 ; i <= len - 1 ; i++ ) {
		int x = int ( s [ i ] ) - 96 ;
		a [ x ] = 1 ;
	}
	for ( int i = 1 ; i <= 26 ; i++ ) {
		if ( a [ i ] == 0 ) {
			char ch = char ( i + 96 ) ;
			cout << ch << endl ;
			flag = true ;
			break ;
		}
	} 
	if ( flag == false ) {
		cout << "None" << endl ;
	}
	return 0 ;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:7:9: error: 'memset' was not declared in this scope
    7 |         memset ( a , 0 , sizeof ( a ) ) ;
      |         ^~~~~~
a.cc:3:1: note: 'memset' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
    2 | #include <cmath>
  +++ |+#include <cstring>
    3 | using namespace std;
a.cc:9:19: error: 'strlen' was not declared in this scope
    9 |         int len = strlen ( s ) ;
      |                   ^~~~~~
a.cc:9:19: note: 'strlen' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
a.cc:18:25: error: 'flag' was not declared in this scope
   18 |                         flag = true ;
      |                         ^~~~
a.cc:22:14: error: 'flag' was not declared in this scope
   22 |         if ( flag == false ) {
      |              ^~~~
Language: C++

#include<iostream>
#include<cstring>
using namespace std;
char s[100000+100];
int a[100]; 
int main(){
	memset(a,0,sizeof(a));
	cin>>s;
	int len=strlen(s);
	for(int i=0;i<=len-1;i++){
		int x=int (s[i])-96;
		a[x]=1;
	}
	for(int i=1;i<=26;i++){
		if(a[i]==0){
			char ch=char(i+96);
			cout<<ch<<endl;
			flag=true;
			break;
		}
	}
	if(flag==false){
		cout<<"None"<<endl;
	}
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:18:25: error: 'flag' was not declared in this scope
   18 |                         flag=true;
      |                         ^~~~
a.cc:22:12: error: 'flag' was not declared in this scope
   22 |         if(flag==false){
      |            ^~~~
Language: C++

import sys

s = sorted(list({i for i in input()}))
a = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"]

for i in range(26):
    if (s[i] != a[i]):
        print(a[i])
        sys.exit()

print("None")


Compiler output:
a.cc:1:1: error: 'import' does not name a type
    1 | import sys
      | ^~~~~~
a.cc:1:1: note: C++20 'import' only available with '-fmodules-ts'
a.cc:3:37: error: expected unqualified-id before ')' token
    3 | s = sorted(list({i for i in input()}))
      |                                     ^
Language: C++

#include<stdio.h>
#include<string.h>

int main(){
    int f[26]={0},len,i,j;
    char simizu[26]={'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','w','x','y','z'};
    char S[100000];

    scanf("%s",%S);
    len=strlen(S);

    for(i=0;i<len;i++){
        for(j=0;j<26;j++){
            if(S[i]==simizu[j]){
                f[j]=1;
            }
        }
    }
    for(i=0;i<26;i++){
        if(f[i]==0){
            printf("%c",simizu[i]);
            break;
        }
    }
    if(i==25){
        printf("None");
    }
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:9:16: error: expected primary-expression before '%' token
    9 |     scanf("%s",%S);
      |                ^
Language: C++

#include <iostream>
using namespace std;

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

    bool a[26] = {false};
    for (int i = 0; i < s.length(); ++i) {
        a[s[i] - 'a'] = true;
    }

    for (int i = 0; i < 26; ++i) {
        if(!a[i]) {
            string ans = 'a' + i;
            cout << ans << endl;
            return 0;
        }
    }
    cout << "None" << endl;

    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:16:30: error: conversion from 'int' to non-scalar type 'std::string' {aka 'std::__cxx11::basic_string<char>'} requested
   16 |             string ans = 'a' + i;
      |                          ~~~~^~~
Language: Java

import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskB solver = new TaskB();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskB {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            char[] a = in.next().toCharArray();
            boolean[] v = new boolean[26];
            for (char x : a) v[x - 'a'] = true;
            for (int i = 0; i < 26; ++i) {
                if (!v[i]) {
                    out.println((char) (i + 'a'));
                    return;
                }
            }
            out.println("None");
        }

    }

    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }


Compiler output:
Main.java:60: error: reached end of file while parsing
        }
         ^
1 error
Language: C

#include <stdio.h>


main ()
{
	char str [] ;
	char alf [26] ;
	char ans ;
	int count ;
	
	count = 0 ;
	while ( count < 26 )
	{
		alf [ count ] = 0 ;
		count++;
	}
	
	scanf ( "%s", str );

	count = 0 ;
	while ( str [ count ] != 0 )
	{
		alf [ str [ count ] - 0x61 ] = 1 ;
		count++;
	}

	count = 0 ;
	while ( count < 26 )
	{
		if ( alf [ count ] == 0 )
		{
			ans = 0x61 + count ;
			printf ( "%c\n", ans );
			return 0 ;
		}
		count++;
	}

	printf ( "None\n" );
	return 0 ;
}


Compiler output:
main.c:4:1: error: return type defaults to 'int' [-Wimplicit-int]
    4 | main ()
      | ^~~~
main.c: In function 'main':
main.c:6:14: error: array size missing in 'str'
    6 |         char str [] ;
      |              ^~~
Language: C

#include <bits/stdc++.h>
using namespace std;
 
int main(){
    char str[100001];
    int i,j,x,ans=0;
    scanf("%s",&str);
    for(j=0;j<26;j++){
        for(i=0;str[i]!='\0';i++){
            x = str[i];
            if(x==(j+97)){
                break;
            }
            if(str[i+1]=='\0'){
                putchar(j+97);
                ans = 1;
                break;
            }
        }
        if(ans==1) break;
    }
    if(ans==0){
        printf("None\n");
    }
    return 0;
}

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

int main(){
    
    string S;
    
    cin >> S;
    
    sort(S.begin(), S.end());
    
    char c;
    c = 97;
    
    
    for(int i = 0; i < S.length(); i++){
        
        if(S[i] != c ){
            cout << c << endl;
            return 0;
        }else if(S[i + 1] != S[i] && i != S.length() - 1){
            if(c == 122){
                cout << "None" << endl;
            }
            c++;
        }else if (i == S.length() - 1){
            c++;
            cout << c << endl;
        }
    }
    
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:11:5: error: 'sort' was not declared in this scope; did you mean 'short'?
   11 |     sort(S.begin(), S.end());
      |     ^~~~
      |     short
Language: C++


#include<iostream>
using namespace std;

int main(){
    
    string S;
    
    cin >> S;
    
    std::sort(S.begin(), S.end());
    
    char c;
    c = 97;
    
    
    for(int i = 0; i < S.length(); i++){
        
        if(S[i] != c ){
            cout << c << endl;
            return 0;
        }else if(S[i + 1] != S[i] && i != S.length() - 1){
            if(c == 122){
                cout << "None" << endl;
            }
            c++;
        }else if (i == S.length() - 1){
            c++;
            cout << c << endl;
        }
    }
    
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:11:10: error: 'sort' is not a member of 'std'; did you mean 'qsort'?
   11 |     std::sort(S.begin(), S.end());
      |          ^~~~
      |          qsort
Language: Java

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String word = sc.next();
        
        List<String> alphabetList = new ArrayList<>();
        for (int i = 97; i < 123; i++) {
            alphabetList.add(String.valueOf((char)i));
        }
        for (int j = 97; j < 123; j++) {
            char containsAlphabet = (char)j;
            if (word.contains(String.valueOf(containsAlphabet))) {
                alphabetList.remove(String.valueOf(containsAlphabet));
            }
        }
        if (alphabetList.isEmpty()) {
           System.out.println("None"); 
        } else {
            System.out.println(alphabetList.get(0));
        }
    }
}

Compiler output:
Main.java:3: error: cannot find symbol
        Scanner sc = new Scanner(System.in);
        ^
  symbol:   class Scanner
  location: class Main
Main.java:3: error: cannot find symbol
        Scanner sc = new Scanner(System.in);
                         ^
  symbol:   class Scanner
  location: class Main
Main.java:6: error: cannot find symbol
        List<String> alphabetList = new ArrayList<>();
        ^
  symbol:   class List
  location: class Main
Main.java:6: error: cannot find symbol
        List<String> alphabetList = new ArrayList<>();
                                        ^
  symbol:   class ArrayList
  location: class Main
4 errors
Language: C++

#include<iostream>
using namespace std;

int main(){
    
    string S;
    
    cin >> S;
    
    sort(S.begin(), S.end());
    
    char c;
    c = 97;
    
    
    for(int i = 0; i < S.length(); i++){
        
        if(S[i] != c ){
            cout << c << endl;
            return 0;
        }else if(S[i + 1] != S[i] && i != S.length() - 1){
            if(c == 122){
                cout << "None" << endl;
            }
            c++;
        }else if (i == S.length() - 1){
            c++;
            cout << c << endl;
        }
    }
    
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:10:5: error: 'sort' was not declared in this scope; did you mean 'short'?
   10 |     sort(S.begin(), S.end());
      |     ^~~~
      |     short
Language: C++

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
int A[25];
char s[10050];
int main()
{
    memset(A,0,sizeof(A));
    gets(s);
    int len=strlen(s);
    for(int i=0;i<len;i++)
    {
        for(char j='a';j<='z';j++)
        {
            if(s[i]==j)
            {
                A[j-'a']=1;
            }
        }
    }

    int flag=0;
    int y;
    for(int i=0;i<=25;i++)
    {
        if(A[i]==0)
        {
           flag=1;
           y=i;
            break;
        }
    }
    if(flag)
    {
        printf("%c\n",y+'a');
    }
    else
    printf("None\n");



}


Compiler output:
a.cc: In function 'int main()':
a.cc:11:5: error: 'gets' was not declared in this scope; did you mean 'getw'?
   11 |     gets(s);
      |     ^~~~
      |     getw
Language: C++


#include<iostream>
using namespace std;

int main(){
    
    string S;
    
    cin >> S;
    
    sort(S.begin(), S.end());
    
    char c;
    c = 97;
    
    
    for(int i = 0; i < S.length(); i++){
        
        if(S[i] != c ){
            cout << c << endl;
            return 0;
        }else if(S[i + 1] != S[i] && i != S.length() - 1){
            if(c == 122){
                cout << "None" << endl;
            }
            c++;
        }else if (i == S.length() - 1){
            c++;
            cout << c << endl;
        }
    }
    
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:11:5: error: 'sort' was not declared in this scope; did you mean 'short'?
   11 |     sort(S.begin(), S.end());
      |     ^~~~
      |     short
Language: C++

#include <stdio.h>
void count(char* str, int occur[], int occur_[])
{
    while(*str) {
        if('a'<=*str&&*str<='z')   occur[*str-'a']++;
        else if('A'<=*str&&*str<='Z')   occur_[*str-'A']++;
        str++;
    }
}
int main()
{
    char s[256];
    int c[26]= {0},C[26]= {0},i;
    gets(s); /* 输入*/
    count(s,c,C);
    for(i=0; i<26; i++){
        if (c[i] > 0)
        printf("%c",(char)('a'+i));
    }
    for(i=0; i<26; i++){
        if (C[i] > 0)
        printf("%c",(char)('A'+i));
    }    
    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:14:5: error: 'gets' was not declared in this scope; did you mean 'getw'?
   14 |     gets(s); /* 输入*/
      |     ^~~~
      |     getw
Language: C++

#include <iostream>
#include <string>
#include <math.h>
#include <iomanip>
#include <cmath>

using namespace std;

int main()
{
    string s;
    long A[26]={0},j=0;
    cin>>s;
    for (long i=0;i<s.length();i++)
    {
        A[s[i]-97]=1;
    }
    while((A[j]==1)&&(j<26))
    {
        j+=A[j];
    }
    if (j==26)
        {
            cout<<"None"<<endl;
        }
            else cout<<(char)(j+97)<<endl;;
    return 0;

Compiler output:
a.cc: In function 'int main()':
a.cc:27:14: error: expected '}' at end of input
   27 |     return 0;
      |              ^
a.cc:10:1: note: to match this '{'
   10 | {
      | ^
Language: C++

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main() {
  char buf[9];
  char *str;
  int length = 0;

  fgets(buf, 9, stdin);
  str = (char *)malloc(sizeof(char) * 8);
  length += 8;
  memcpy(str, buf, 8);
  while(strlen(buf) >= 8) {
    fgets(buf, 9, stdin);
    length += 8;
    str = realloc(str, sizeof(char) * length);
    memcpy((str + (length - 8)), buf, 8);
  }

  int flag;
  int i;
  for(i=0;i<26;i++) {
    flag = 0;
    int j;
    for(j=0;;j++) {
      char chr = str[j];
      if(chr == 0x0d || chr == 0x0a || chr == 0x1a || chr == 0xff || chr == 0x00) break;
      //printf("0x%02X ", str[j] & 0x000000ff);
      if(str[j] == 'a' + (char)i) {
	flag = 1;
      }
    }
    if(flag == 0) {
      putchar('a' + (char)i);
      break;
    }
  }
  if(flag != 0) printf("None");
  /*
  for(i=0;i<length;i++) {
    putchar(str[i]);
  }
  printf("\nlength=%d\n", length);
  */
  free(str);
  return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:17:18: error: invalid conversion from 'void*' to 'char*' [-fpermissive]
   17 |     str = realloc(str, sizeof(char) * length);
      |           ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |                  |
      |                  void*
Language: C++

#include <iostream>
#include <stdio.h>
#include <string.h>
using namespace std;


int main()
{
	string s;
	cin>>s;
	int n=s.length();
	int a[26];
	for(int i=0;i<26;i++)
	{
		a[i]=0;
	}
	for(int i=0;i<n;i++)
	{
		a[s[i]-97]=1;
	}
	for(int i=0;i<26;i++)
	{
		if(a[i]==0)
		{
			cout<<s[a[i]+98]<<endl;
			return 0;
		}
	}
	cout<<"None"<<endl;
	return 0;
}
20:51:43
好好睡觉好好吃饭 2017/8/20 20:51:43


对方已成功接收了您发送的离线文件“ascii.jpg”(367.46KB)。
21:02:35
刘景祺 2017/8/20 21:02:35
#include <iostream>
#include <stdio.h>
#include <string>

using namespace std;

int main()
{
	string s;
	cin>>s;
	int n=s.length();
	char g[n],c;
	int a[26];
	for(int i=0;i<26;i++)
	{
		a[i]=0;
	}
	for(int i=0;i<n;i++)
	{
		a[s[i]-97]=1;
		g[i]=s[i];
	}
	for(int i=0;i<26;i++)
	{
		if(a[i]==0)
		{
			c=i+97;
			cout<<c<<endl;
			return 0;
		}
	}
	cout<<"None"<<endl;
	return 0;
}

Compiler output:
a.cc:36:1: error: extended character “ is not valid in an identifier
   36 | 对方已成功接收了您发送的离线文件“ascii.jpg”(367.46KB)。
      | ^
a.cc:36:40: error: extended character ” is not valid in an identifier
   36 | 对方已成功接收了您发送的离线文件“ascii.jpg”(367.46KB)。
      |                                        ^
a.cc:36:54: error: extended character 。 is not valid in an identifier
   36 | 对方已成功接收了您发送的离线文件“ascii.jpg”(367.46KB)。
      |                                                      ^
a.cc:32:1: error: expected unqualified-id before numeric constant
   32 | 20:51:43
      | ^~
a.cc:45:5: error: redefinition of 'int main()'
   45 | int main()
      |     ^~~~
a.cc:7:5: note: 'int main()' previously defined here
    7 | int main()
      |     ^~~~
Language: C++

#include<iostream>
#include<cstring>
using namespace std;
char s[110000];
int len;
bool y[26];
int main(){
	for(int k=0;k<=26;k++){
	y[k]=true;
}
	cin>>s;
	len=strlen(s);
	for(int i='a';i<='z';i++){
		for(int j=0;j<=len;j++){
			if(s[j]==i){
				y[i]=false;
			}
		}
	}
	for(char u='a';u<='z';u++){
		if(y[u-50]==true){
			cout<<u<<endl;
			break;
		}
	}
	if(y[u-50]==false&&y[u-49]==false&&y[u-48]==false&&y[u-47]==false&&y[u-46]==false&&y[u-45]==false&&y[u-44]==false&&y[u-43]==false&&y[u-42]==false&&y[u-41]==false&&y[u-40]==false&&y[u-49]==false&&y[u-39]==false&&y[u-38]==false&&y[u-37]==false&&y[u-36]==false&&y[u-35]==false&&y[u-34]==false&&y[u-33]==false&&y[u-32]==false&&y[u-31]==false&&y[u-30]==false&&y[u-29]==false&&y[u-28]==false&&y[u-27]==false&&y[u-26]==false&&y[u-25]==false){
	cout<<"None";
	}
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:26:14: error: 'u' was not declared in this scope
   26 |         if(y[u-50]==false&&y[u-49]==false&&y[u-48]==false&&y[u-47]==false&&y[u-46]==false&&y[u-45]==false&&y[u-44]==false&&y[u-43]==false&&y[u-42]==false&&y[u-41]==false&&y[u-40]==false&&y[u-49]==false&&y[u-39]==false&&y[u-38]==false&&y[u-37]==false&&y[u-36]==false&&y[u-35]==false&&y[u-34]==false&&y[u-33]==false&&y[u-32]==false&&y[u-31]==false&&y[u-30]==false&&y[u-29]==false&&y[u-28]==false&&y[u-27]==false&&y[u-26]==false&&y[u-25]==false){
      |              ^
Language: C++

#include <iostream>
#include<sstream>
#include<vector>
#include<iterator>
using namespace std;

int main(void)
{
	string S;
	cin >> S;

	vector<int> cnt(26, 0);
	for(auto it=S.begin(); it!=S.end(); it++)
		cnt[*it-'a']++;

	auto pos = find(cnt.begin(), cnt.end(), 0);
	string ret = "";
	if(pos == cnt.end())
		ret = "None";
	else
	{
		int d = pos - cnt.begin();
		char ch = 'a' + d;
		ret = ch;
	}

	cout << ret << endl;

	return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:16:24: error: no matching function for call to 'find(std::vector<int>::iterator, std::vector<int>::iterator, int)'
   16 |         auto pos = find(cnt.begin(), cnt.end(), 0);
      |                    ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/bits/locale_facets.h:48,
                 from /usr/include/c++/14/bits/basic_ios.h:37,
                 from /usr/include/c++/14/ios:46,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/streambuf_iterator.h:435:5: note: candidate: 'template<class _CharT2> typename __gnu_cxx::__enable_if<std::__is_char<_CharT2>::__value, std::istreambuf_iterator<_CharT> >::__type std::find(istreambuf_iterator<_CharT>, istreambuf_iterator<_CharT>, const _CharT2&)'
  435 |     find(istreambuf_iterator<_CharT> __first,
      |     ^~~~
/usr/include/c++/14/bits/streambuf_iterator.h:435:5: note:   template argument deduction/substitution failed:
a.cc:16:24: note:   '__gnu_cxx::__normal_iterator<int*, std::vector<int> >' is not derived from 'std::istreambuf_iterator<_CharT>'
   16 |         auto pos = find(cnt.begin(), cnt.end(), 0);
      |                    ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
Language: C

#include<stdio.h>
#include<string.h>
int main(){
    int len;
    char str1[100000];
    char str2[26]={"abcdefghijklmnopqrstuvwxyz"};
    scanf("%s",str);
    len=strlen(str1);
    for(int i=0;i<strlen;i++){
        for(int j=0;j<26;j++){
            if(str1[i]==str2[j]){
                str2[j]='0';
            }
        }
    }
    for(int k=0;k<26;k++){
        if(str2[k]!='0'){
            printf("%c",str2[k]);
            break;
        }else if(k==25){
            printf("None");
        }
    }
    return 0;
}

Compiler output:
main.c: In function 'main':
main.c:7:16: error: 'str' undeclared (first use in this function); did you mean 'str2'?
    7 |     scanf("%s",str);
      |                ^~~
      |                str2
main.c:7:16: note: each undeclared identifier is reported only once for each function it appears in
main.c:9:18: warning: comparison between pointer and integer
    9 |     for(int i=0;i<strlen;i++){
      |                  ^
Language: C++

#include<cstdio>
#include<iostream>
#include<cmath>
using namespace std;
int main()
{
    char s[10005];
    int a[150],i;
    cin>>s;
    int len=strlen(s);
    for(i=0;i<len;i++)
    {
        if(a[s[i]]==0)
        a[s[i]]=1;
    }
    for(i='a';i<='z';i++)
    {
        if(a[i]==0)
        {printf("%c\n",i);break;}
    }
    if(i=='z'+1)
    printf("None\n");
}

Compiler output:
a.cc: In function 'int main()':
a.cc:10:13: error: 'strlen' was not declared in this scope
   10 |     int len=strlen(s);
      |             ^~~~~~
a.cc:4:1: note: 'strlen' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
    3 | #include<cmath>
  +++ |+#include <cstring>
    4 | using namespace std;
Language: C++

int main() {

	char str[100001];
	bool exist[26];

	scanf("%s", str);
	int length = strlen(str);
	for(int L10 = 0; L10 < 26; L10++) {
		exist[L10] = false;
	}

	for(int L10 = 0; L10 < length; L10++) {
		exist[(str[L10] - 'a')] = true;
	}

	for(int L10 = 0; L10 < 26; L10++) {
		if(exist[L10])continue;
		char result[2];
		result[0] = L10 + 'a';
		result[1] = '\0';

		printf(result);
		return 0;
	}
	printf("None");
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:6:9: error: 'scanf' was not declared in this scope
    6 |         scanf("%s", str);
      |         ^~~~~
a.cc:7:22: error: 'strlen' was not declared in this scope
    7 |         int length = strlen(str);
      |                      ^~~~~~
a.cc:1:1: note: 'strlen' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
  +++ |+#include <cstring>
    1 | int main() {
a.cc:22:17: error: 'printf' was not declared in this scope
   22 |                 printf(result);
      |                 ^~~~~~
a.cc:1:1: note: 'printf' is defined in header '<cstdio>'; this is probably fixable by adding '#include <cstdio>'
  +++ |+#include <cstdio>
    1 | int main() {
a.cc:25:9: error: 'printf' was not declared in this scope
   25 |         printf("None");
      |         ^~~~~~
a.cc:25:9: note: 'printf' is defined in header '<cstdio>'; this is probably fixable by adding '#include <cstdio>'
Language: C

#include <stdio.h>


main ()
{
	char str [256] ;
	char alf [26] ;
	char ans ;
	int count ;
	
	count = 0 ;
	while ( count < 26 )
	{
		alf [ count ] = 0 ;
		count++;
	}
	
	scanf ( "%s", str[] );

	count = 0 ;
	while ( str [ count ] != 0 )
	{
		alf [ str [ count ] - 0x61 ] = 1 ;
		count++;
	}

	count = 0 ;
	while ( count < 26 )
	{
		if ( alf [ count ] == 0 )
		{
			ans = 0x61 + count ;
			printf ( "%c\n", ans );
			return 0 ;
		}
		count++;
	}

	printf ( "None\n" );
	return 0 ;
}


Compiler output:
main.c:4:1: error: return type defaults to 'int' [-Wimplicit-int]
    4 | main ()
      | ^~~~
main.c: In function 'main':
main.c:18:27: error: expected expression before ']' token
   18 |         scanf ( "%s", str[] );
      |                           ^
Language: C++

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

int main()
{
	string s;
	cin>>s;
	bool a[27];
	for(int i=1;i<=26;i++)
	{
		a[i]=false;
	}
	int len=s.size();
	for(int i=0;i<len;i++)
	{
		char b=s.substr(i,1);
		a[(int)(b-96)]=true;
	} 
	int f=0,k=28;
	for(int i=1;i<=26;i++)
	{
		if(a[i]==false && i<k) {k=i;f=1;} 
	} 
	if(f==1) cout<<char(k+96);
	else cout<<"None"; 
} 

Compiler output:
a.cc: In function 'int main()':
a.cc:17:32: error: cannot convert 'std::__cxx11::basic_string<char>' to 'char' in initialization
   17 |                 char b=s.substr(i,1);
      |                        ~~~~~~~~^~~~~
      |                                |
      |                                std::__cxx11::basic_string<char>
Language: C++

#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<cstdlib>
#include<string.h>
#include<stdio.h>
#include<string.h> 
#define MAXN (int)1e5+10
using namespace std;

char s[MAXN];

int main()
{
	bool al[200];
	memset(al,false,sizeof(al));
	gets(s);
	for(int i=0;i<strlen(s);i++)
	{
		al[s[i]]=true;
	}
	for(char i='a';i<='z';i++)
	{
		if(!al[i])
		{
			cout<<char(i)<<endl;
			return 0;
		}
	}
	cout<<"None"<<endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:18:9: error: 'gets' was not declared in this scope; did you mean 'getw'?
   18 |         gets(s);
      |         ^~~~
      |         getw
Language: C++

#include<iostream>
#include<cstring>
using namespace std;
char a[100010];
bool num[27];
int main()
{
	memset(num,false,sizeof(num));
	gets(a);
	int len=strlen(a);
	for(int i=0;i<len;i++)
	{
		num[int(a[i])-96]=true;
	}
	int i=1;
	while(num[i]==true&&i<26)
	{
		i++;
	}
	if(num[i]==false)cout<<char(i+96);else cout<<"None";
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:9:9: error: 'gets' was not declared in this scope; did you mean 'getw'?
    9 |         gets(a);
      |         ^~~~
      |         getw
Language: C++

#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<cstdlib>
#include<string>
#include<stdio.h>
#include<string.h> 
#define MAXN (int)1e5+10
using namespace std;

char s[MAXN];

int main()
{
	bool al[200];
	memset(al,false,sizeof(al));
	gets(s);
	for(int i=0;i<strlen(s);i++)
	{
		al[s[i]]=true;
	}
	for(char i='a';i<='z';i++)
	{
		if(!al[i])
		{
			cout<<char(i)<<endl;
			return 0;
		}
	}
	cout<<"None"<<endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:18:9: error: 'gets' was not declared in this scope; did you mean 'getw'?
   18 |         gets(s);
      |         ^~~~
      |         getw
Language: C++

#include <cstdio>
#include <iostream>
#include <cmath>
#include <cstring>
const int maxn = 1e5 + 10;
using namespace std;

int main()
{
    char a[maxn];
    char b[27];
    for (int i = 0; i < 26; i++)
        b[i] = 'a' + i;
    gets(a);
    int ok = 1, h = 0;
    for (int i = 0; i < 26; i++) {
        for (int j = 0; j < strlen(a); j++) {
            if (a[j] == b[i]) {
                ok = 0;
                break;
            }
        }
            if (!ok)
                ok = 1;
            else {
                    cout << b[i] << endl;
                    h = 1;
                    break;
                }
    }
    if (!h)
        cout << "None" << endl;
    return 0;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:14:5: error: 'gets' was not declared in this scope; did you mean 'getw'?
   14 |     gets(a);
      |     ^~~~
      |     getw
Language: C++

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

int main() {
	string S;
	cin >> S;
	bool str[26];
	for (int i = 0; i < 26; i++)
		str[i] = true;

	char ch[26];
	for (int i = 0, j = 97; i < 26; i++, j++)
		ch[i] = j;

	int len = strlen(&S[0]);
	bool flag = true;
	for (int i = 0; i < len; i++) {
		for (int j = 0; j < 26; j++)
			if (S[i] == ch[j]) {
				str[j] = false;
			}
	}
	for (int i = 0; i < 26; i++)
		if (str[i]) {
			flag = false;
			printf("%c\n", ch[i]);
			break;
		}
	if (flag)
		printf("None\n");

}


Compiler output:
a.cc: In function 'int main()':
a.cc:17:19: error: 'strlen' was not declared in this scope
   17 |         int len = strlen(&S[0]);
      |                   ^~~~~~
a.cc:3:1: note: 'strlen' is defined in header '<cstring>'; this is probably fixable by adding '#include <cstring>'
    2 | #include <cstdio>
  +++ |+#include <cstring>
    3 | #include <string>
Language: C

#include<string.h>
#include<stdio.h>
#define MAXN (int)1e5+10
using namespace std;

char s[MAXN];

int main()
{
	bool al[200];
	memset(al,false,sizeof(al));
	gets(s);
	for(int i=0;i<strlen(s);i++)
	{
		al[(int)s[i]]=true;
	}
	for(int i='a';i<='z';i++)
	{
		if(!al[i])
		{
			printf("%c\n",char(i));
			return 0;
		}
	}
	printf("None\n");
	return 0;
}

Compiler output:
main.c:4:1: error: unknown type name 'using'
    4 | using namespace std;
      | ^~~~~
main.c:4:17: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'std'
    4 | using namespace std;
      |                 ^~~
main.c: In function 'main':
main.c:10:9: error: unknown type name 'bool'
   10 |         bool al[200];
      |         ^~~~
main.c:3:1: note: 'bool' is defined in header '<stdbool.h>'; this is probably fixable by adding '#include <stdbool.h>'
    2 | #include<stdio.h>
  +++ |+#include <stdbool.h>
    3 | #define MAXN (int)1e5+10
main.c:11:19: error: 'false' undeclared (first use in this function)
   11 |         memset(al,false,sizeof(al));
      |                   ^~~~~
main.c:11:19: note: 'false' is defined in header '<stdbool.h>'; this is probably fixable by adding '#include <stdbool.h>'
main.c:11:19: note: each undeclared identifier is reported only once for each function it appears in
main.c:12:9: error: implicit declaration of function 'gets'; did you mean 'fgets'? [-Wimplicit-function-declaration]
   12 |         gets(s);
      |         ^~~~
      |         fgets
main.c:15:31: error: 'true' undeclared (first use in this function)
   15 |                 al[(int)s[i]]=true;
      |                               ^~~~
main.c:15:31: note: 'true' is defined in header '<stdbool.h>'; this is probably fixable by adding '#include <stdbool.h>'
main.c:21:39: error: expected expression before 'char'
   21 |                         printf("%c\n",char(i));
      |                                       ^~~~