2168. Square punch

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

const int N = 101, M = 101;

bool gr[N][M];

int n,m;

bool used[N][M];

int DX[] = {0,0,1,-1};
int DY[] = {-1,1,0,0};

void dfs(int x,int y)
{
    int xn, yn;
    used[x][y] = true;
    for(int i = 0 ; i < 4 ; ++i)
    {
        xn = x + DX[i], yn = y + DY[i];
        if(xn >= 0 && xn < n && yn >= 0 && yn < m && !gr[xn][yn] && !used[xn][yn])
            dfs(xn,yn);
    }

    return;
}

signed main()
{
    scanf("%d %d",&n,&m);

    for(int i = 0 ; i < n ; ++i)
    {
        for(int j = 0 ; j < m ; ++j)
        {
            scanf("%d",&gr[i][j]);
        }
    }

    int c = 0;

    for(int i = 0 ; i < n ; ++i)
    {
        for(int j = 0 ; j < m ; ++j)
        {
            if(!used[i][j] && !gr[i][j])
            {
                dfs(i,j);
                c++;
            }
        }
    }

    printf("%d",c);

    return 0;
}