Language: C++

#include <bits/stdc++.h>
using namespace std;
#define N 2001

int n, m, sum[N][N], ngang[N][N], doc[N][N], Q;
int x1, y1, x2, y2;
char a[N][N];

// Tinh số thành pahanf liên thông của HCN giới hạn bởi 4 đường x1 y1 x2 y2;
// Theo đề bài : Graph các đỉnh xanh LÀ 1 CÂY
// =>> Số thành phần liên thông của cây : = số đình - số cạnh
// => Duy trì mảng sum (i,  j) : Tổng số đỉnh trong khoảng HCN (1, 1) -> (i, j)
// => Duy trì mảng ngang (i,  j) : Tổng số cạnh ngang trong khoảng HCN (1, 1) -> (i, j)
// => Duy trì mảng doc (i,  j) : Tổng số cạnh dọc trong khoảng HCN (1, 1) -> (i, j)


void Init()
{
    cin >> n >> m >> Q;
    for(int i = 1; i <= n; i++)
        for(int j = 1; j <= m; j++)
            sum[i][j] = 0, doc[i][j] = 0, ngang[i][j] = 0;
    for(int i = 1; i <= n; i++)
        for(int j = 1; j <= m; j++)
        {
            cin >> a[i][j];
            sum[i][j]     = sum[i][j - 1] + sum[i - 1][j] - sum[i - 1][j - 1] + (a[i][j] - '0');                            // a(i,j) = 1 khi dinh> mau xanh
            ngang[i][j]   = ngang[i][j - 1] + ngang[i - 1][j] - ngang[i - 1][j - 1] + (a[i][j] == '1' && a[i][j - 1] == '1' ? 1 : 0); // Nếu có cạnh nối từ a(i,j) xuống HCN(1,1) (i, j - 1) thì số cạnh tăng 1
            doc[i][j]     = doc[i][j - 1] + doc[i - 1][j] - doc[i - 1][j - 1] + (a[i][j] == '1' && a[i - 1][j] == '1' ? 1 : 0);       // Nếu có cạnh nối từ a(i,j) về HCN(1,1) (i - 1, j) thì số cạnh tăng 1
        }
}

void Solve()
{
    for(int i = 1; i <= Q; i++)
    {

        cin >> x1 >> y1 >> x2 >> y2;

        int cnt_dinh  = sum[x2][y2] - sum[x1 - 1][y2] - sum[x2][y1 - 1] + sum[x1 - 1][y1 - 1];
        int cnt_ngang = ngang[x2][y2] - ngang[x1 - 1][y2] - ngang[x2][y1] + ngang[x1 - 1][y1];
        int cnt_doc   = doc[x2][y2] - doc[x1][y2] - doc[x2][y1 - 1] + doc[x1][y1 - 1];
            // Vs đếm ngang thì sẽ tính giới hạn cột từ x1 + 1 đến x2 để tránh cột x1 liên thông svs bên ngoài, tương tự vs đếm dọc

        cout << cnt_dinh - cnt_doc - cnt_ngang << endl;
    }
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    //freopen("NUSKE.INP", "r", stdin);
  // freopen("NUSKE.OUT", "w", stdout);

    Init();
    Solve();
}




Compiler output:
a.cc:6:9: error: 'int y1' redeclared as different kind of entity
    6 | int x1, y1, x2, 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 Solve()':
a.cc:38:19: error: no match for 'operator>>' (operand types are 'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} and 'double(double) noexcept')
   38 |         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:38:22: error: cannot bind non-const lvalue reference of type 'bool&' to a value of type 'double (*)(double) noexcept'
   38 |         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:38:22: error: invalid conversion from 'double (*)(double) noexcept' to 'short int' [-fpermissive]
   38 |         cin >> x1 >> y1 >> x2 >> y2;
      |                      ^~
      |                      |
      |                      double (*)(double) noexcept
a.cc:38:22: 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:38:22: error: invalid conversion from 'double (*)(double) noexcept' to 'short unsigned int' [-fpermissive]
   38 |         cin >> x1 >> y1 >> x2 >> y2;
      |                      ^~
      |                      |
      |                      double (*)(double) noexcept
a.cc:38:22: 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:38:22: error: invalid conversion from 'double (*)(double) noexcept' to 'int' [-fpermissive]
   38 |         cin >> x1 >> y1 >> x2 >> y2;
      |                      ^~
      |                      |
      |                      double (*)(double) noexcept
a.cc:38:22: 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:38:22: error: invalid conversion from 'double (*)(double) noexcept' to 'unsigned int' [-fpermissive]
   38 |         cin >> x1 >> y1 >> x2 >> y2;
      |                      ^~
      |                      |
      |                      double (*)(double) noexcept
a.cc:38:22: 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:38:22: error: invalid conversion from 'double (*)(double) noexcept' to 'long int' [-fpermissive]
   38 |         cin >> x1 >> y1 >> x2 >> y2;
      |                      ^~
      |                      |
      |                      double (*)(double) noexcept
a.cc:38:22: 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:38:22: error: invalid conversion from 'double (*)(double) noexcept' to 'long unsigned int' [-fpermissive]
   38 |         cin >> x1 >> y1 >> x2 >> y2;
      |                      ^~
      |                      |
      |                      double (*)(double) noexcept
a.cc:38:22: 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:38:22: error: invalid conversion from 'double (*)(double) noexcept' to 'long long int' [-fpermissive]
   38 |         cin >> x1 >> y1 >> x2 >> y2;
      |                      ^~
      |                      |
      |                      double (*)(double) noexcept
a.cc:38:22: 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:38:22: error: invalid conversion from 'double (*)(double) noexcept' to 'long long unsigned int' [-fpermissive]
   38 |         cin >> x1 >> y1 >> x2 >> y2;
      |                      ^~
      |                      |
      |                      double (*)(double) noexcept
a.cc:38:22: 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:38:22: error: invalid conversion from 'double (*)(double) noexcept' to 'void*' [-fpermissive]
   38 |         cin >> x1 >> y1 >> x2 >> y2;
      |                      ^~
      |                      |
      |                      double (*)(double) noexcept
a.cc:38:22: 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:38:22: 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]
   38 |         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::basic_istream<char>; __ios_type = std::basic_ios<char>]' (near match)
  126 |       operator>>(__ios_type& (*__pf)(__ios_type&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:126:7: note:   conversion of