C++10分求助

#include <iostream>
using namespace std;

char s[1002][1002];
int n, m, b[100002][3], f[1002][1002], visit[1002][1002] = {0};

int dfs(int x, int y) {
    if (visit[x][y])
        return 0;
    
    visit[x][y] = 1;
    int cnt = 1;
    
    int nx[4] = {-1, 0, 1, 0};
    int ny[4] = {0, 1, 0, -1};
    
    for (int i = 0; i < 4; i++) {
        int fx = nx[i] + x;
        int fy = ny[i] + y;
        
        if (fx >= 1 && fy >= 1 && fx <= n && fy <= n) {
            if (s[x][y] == '0') {
                if (s[fx][fy] == '1') {
                    cnt += dfs(fx, fy);
                }
            } else {
                if (s[fx][fy] == '0') {
                    cnt += dfs(fx, fy);
                }
            }
        }
    }
    
    return cnt;
}

int main() {
    cin >> n >> m;
    
    for (int i = 1; i <= n; i++) {
        cin >> (s[i] + 1);
    }
    
    for (int i = 1; i <= m; i++) {
        cin >> b[i][1] >> b[i][2];
    }
    
    for (int i = 1; i <= m; i++) {
        int x = b[i][1];
        int y = b[i][2];
        
        int cnt = dfs(x, y);
        cout << cnt << "\n";
    }
    
    return 0;
}