Language: C++

#include <bits/stdc++.h>
#define mem(a,b) memset(a,b,sizeof(a))
using namespace std;
int n, m, Q;
bool vis[2002][2002];
int G[2002][2002];
int g[2002][2002];
int x1,x2,y1,y2;
int cnt;
void dfs(int i, int j){
    if(vis[i][j] || G[i][j] == 0) return;
    if(i<x1||i>x2||j<y1||j>y2) return;
    vis[i][j] = true;
    dfs(i+1,j);
    dfs(i-1,j);
    dfs(i,j+1);
    dfs(i,j-1);
}
int main(){

    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n >> m >> Q;
    string s;
    for(int i = 1; i <= n; i++){
        cin >> s;
        for(int j = 1; j <= m; j++){
            G[i][j] = s[j-1] == '0' ? 0 : 1;
 //           if(G[i][j] == 0) g[i][j] = 0; 
        }

    }    
    for(int q = 1; q <= Q; q++){
        cin >> x1 >> y1 >> x2 >> y2;
        if(x1 > x2) swap(x1, x2);
        if(y1 > y2) swap(y1, y2);
        mem(vis,false);
        cnt = 0;
        for(int i = x1; i <= x2; i++){
            for(int j = y1; j <= y2; j++){
                if(!vis[i][j] && G[i][j] != 0)
                    dfs(i,j),cnt++;
            }
        }
        cout << cnt << endl;
    }
     return 0;
}

Compiler output:
a.cc:8:11: error: 'int y1' redeclared as different kind of entity
    8 | int x1,x2,y1,y2;
      |           ^~
In file included from /usr/include/features.h:523,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/os_defines.h:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/c++config.h:683,
                 from /usr/include/c++/14/cassert:43,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:33,
                 from a.cc:1:
/usr/include/x86_64-linux-gnu/bits/mathcalls.h:257:1: note: previous declaration 'double y1(double)'
  257 | __MATHCALL (y1,, (_Mdouble_));
      | ^~~~~~~~~~
a.cc: In function 'void dfs(int, int)':
a.cc:12:21: error: ISO C++ forbids comparison between pointer and integer [-fpermissive]
   12 |     if(i<x1||i>x2||j<y1||j>y2) return;
      |                    ~^~~
a.cc: In function 'int main()':
a.cc:34:19: error: no match for 'operator>>' (operand types are 'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} and 'double(double) noexcept')
   34 |         cin >> x1 >> y1 >> x2 >> y2;
      |         ~~~~~~~~~ ^~ ~~
      |             |        |
      |             |        double(double) noexcept
      |             std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}
In file included from /usr/include/c++/14/sstream:40,
                 from /usr/include/c++/14/complex:45,
                 from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127:
/usr/include/c++/14/istream:170:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  170 |       operator>>(bool& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:170:7: note:   conversion of argument 1 would be ill-formed:
a.cc:34:22: error: cannot bind non-const lvalue reference of type 'bool&' to a value of type 'double (*)(double) noexcept'
   34 |         cin >> x1 >> y1 >> x2 >> y2;
      |                      ^~
/usr/include/c++/14/istream:174:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  174 |       operator>>(short& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:174:7: note:   conversion of argument 1 would be ill-formed:
a.cc:34:22: error: invalid conversion from 'double (*)(double) noexcept' to 'short int' [-fpermissive]
   34 |         cin >> x1 >> y1 >> x2 >> y2;
      |                      ^~
      |                      |
      |                      double (*)(double) noexcept
a.cc:34:22: error: cannot bind rvalue '(short int)y1' to 'short int&'
/usr/include/c++/14/istream:177:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  177 |       operator>>(unsigned short& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:177:7: note:   conversion of argument 1 would be ill-formed:
a.cc:34:22: error: invalid conversion from 'double (*)(double) noexcept' to 'short unsigned int' [-fpermissive]
   34 |         cin >> x1 >> y1 >> x2 >> y2;
      |                      ^~
      |                      |
      |                      double (*)(double) noexcept
a.cc:34:22: error: cannot bind rvalue '(short unsigned int)y1' to 'short unsigned int&'
/usr/include/c++/14/istream:181:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  181 |       operator>>(int& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:181:7: note:   conversion of argument 1 would be ill-formed:
a.cc:34:22: error: invalid conversion from 'double (*)(double) noexcept' to 'int' [-fpermissive]
   34 |         cin >> x1 >> y1 >> x2 >> y2;
      |                      ^~
      |                      |
      |                      double (*)(double) noexcept
a.cc:34:22: error: cannot bind rvalue '(int)y1' to 'int&'
/usr/include/c++/14/istream:184:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  184 |       operator>>(unsigned int& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:184:7: note:   conversion of argument 1 would be ill-formed:
a.cc:34:22: error: invalid conversion from 'double (*)(double) noexcept' to 'unsigned int' [-fpermissive]
   34 |         cin >> x1 >> y1 >> x2 >> y2;
      |                      ^~
      |                      |
      |                      double (*)(double) noexcept
a.cc:34:22: error: cannot bind rvalue '(unsigned int)y1' to 'unsigned int&'
/usr/include/c++/14/istream:188:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  188 |       operator>>(long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:188:7: note:   conversion of argument 1 would be ill-formed:
a.cc:34:22: error: invalid conversion from 'double (*)(double) noexcept' to 'long int' [-fpermissive]
   34 |         cin >> x1 >> y1 >> x2 >> y2;
      |                      ^~
      |                      |
      |                      double (*)(double) noexcept
a.cc:34:22: error: cannot bind rvalue '(long int)y1' to 'long int&'
/usr/include/c++/14/istream:192:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  192 |       operator>>(unsigned long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:192:7: note:   conversion of argument 1 would be ill-formed:
a.cc:34:22: error: invalid conversion from 'double (*)(double) noexcept' to 'long unsigned int' [-fpermissive]
   34 |         cin >> x1 >> y1 >> x2 >> y2;
      |                      ^~
      |                      |
      |                      double (*)(double) noexcept
a.cc:34:22: error: cannot bind rvalue '(long unsigned int)y1' to 'long unsigned int&'
/usr/include/c++/14/istream:199:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  199 |       operator>>(long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:199:7: note:   conversion of argument 1 would be ill-formed:
a.cc:34:22: error: invalid conversion from 'double (*)(double) noexcept' to 'long long int' [-fpermissive]
   34 |         cin >> x1 >> y1 >> x2 >> y2;
      |                      ^~
      |                      |
      |                      double (*)(double) noexcept
a.cc:34:22: error: cannot bind rvalue '(long long int)y1' to 'long long int&'
/usr/include/c++/14/istream:203:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  203 |       operator>>(unsigned long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:203:7: note:   conversion of argument 1 would be ill-formed:
a.cc:34:22: error: invalid conversion from 'double (*)(double) noexcept' to 'long long unsigned int' [-fpermissive]
   34 |         cin >> x1 >> y1 >> x2 >> y2;
      |                      ^~
      |                      |
      |                      double (*)(double) noexcept
a.cc:34:22: error: cannot bind rvalue '(long long unsigned int)y1' to 'long long unsigned int&'
/usr/include/c++/14/istream:328:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  328 |       operator>>(void*& __p)
      |       ^~~~~~~~
/usr/include/c++/14/istream:328:7: note:   conversion of argument 1 would be ill-formed:
a.cc:34:22: error: invalid conversion from 'double (*)(double) noexcept' to 'void*' [-fpermissive]
   34 |         cin >> x1 >> y1 >> x2 >> y2;
      |                      ^~
      |                      |
      |                      double (*)(double) noexcept
a.cc:34:22: error: cannot bind rvalue '(void*)y1' to 'void*&'
/usr/include/c++/14/istream:122:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__istream_type& (*)(__istream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  122 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:122:7: note:   conversion of argument 1 would be ill-formed:
a.cc:34:22: error: invalid conversion from 'double (*)(double) noexcept' to 'std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&)' {aka 'std::basic_istream<char>& (*)(std::basic_istream<char>&)'} [-fpermissive]
   34 |         cin >> x1 >> y1 >> x2 >> y2;
      |                      ^~
      |                      |
      |                      double (*)(double) noexcept
/usr/include/c++/14/istream:126:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__ios_type& (*)(__ios_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::bas