70分TLE求助。#3#10#11没过

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

int n, m, v[1005][1005];
char a[1005][1005];
int cn[100005];

void dfs(int x, int y, int num, int p) {
    if (x == 0 || y == 0 || x == n + 1 || y == n + 1 || v[x][y] == 1 || num == a[x][y]) return;
    if (!v[x][y]) {
        v[x][y] = 1;
        cn[p]++;
        dfs(x + 1, y, a[x][y], p);
        dfs(x, y + 1, a[x][y], p);
        dfs(x - 1, y, a[x][y], p);
        dfs(x, y - 1, a[x][y], p);
    }
}

int main() {
    cin >> n >> m;
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            cin >> a[i][j];
        }
    }
    int x1, y1;
    for (int i = 0; i < m; i++) {
        cin >> x1 >> y1;
        dfs(x1, y1, a[x1][y1] - '0', i);
        cout << cn[i] << endl;
        memset(v, 0, sizeof(v));
    }
    return 0;
}