求助大佬，3TLE，1，10RE

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

const int N = 1010;
char loc[N][N];
int n, m, ans, cou, res[N][N];
int dx[] = {-1, 0, 1, 0};
int dy[] = {0, -1, 0, 1};
bool st[N][N];
struct tem {int x1, y1;} temp[100010];

void dfs(int x, int y) {
    for (int i = 0; i < 4; i++) {
        int a = x + dx[i], b = y + dy[i];

        if (a < 1 || a > n || b < 1 || b > n) continue;
        if (st[a][b]) continue;
        if (loc[a][b] == loc[x][y]) continue;

        st[a][b] = true;
        ans++;
        cou++;
        temp[cou].x1 = a, temp[cou].y1 = b;
        dfs(a, b);
    }
}

int main() {
    cin >> n >> m;
    int x=0,y=0;
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++)
            cin >> loc[i][j];
    }
    memset(res, 0, sizeof(res));
    for (int i = 1; i <= m; i++) {
        cin >> x >> y;
        if (res[x][y]) {
            cout << res[x][y] << endl;
        } else {
            ans = 1; cou = 0;
            memset(st, false, sizeof(st)); // 重置 st 数组
            st[x][y] = true;
            dfs(x, y);
            temp[0].x1 = x, temp[0].y1 = y; 
            for (int j = 0; j <= cou; j++) { 
                res[temp[j].x1][temp[j].y1] = ans;
            }
            cout << res[x][y] << endl;
        }
    }
    return 0;
}