反打帅童

帅童不信能用bfs，那我就写一个AC的bfs给他看看

#include <bits/stdc++.h>
using namespace std;
constexpr int dirs[][2]{1, 0, 0, 1, -1, 0, 0, -1};
string grid[105];
int n, m;
int bfs(int a, int b) {
    int cnt = 1;
    bool vis[105][105]{};
    queue <pair <int, int>> q;
    q.emplace(a, b);
    vis[a][b] = 1;
    while (! q.empty()) {
        auto [x, y] = q.front(); q.pop();
        int flag = grid[x][y] - '0';
        for (auto &[dx, dy] : dirs) {
            int nx = x + dx, ny = y + dy;
            if (nx < 1 || ny < 1 || nx > n || ny > n) continue;
            if (vis[nx][ny]) continue;
            if (grid[nx][ny] - '0' == flag) continue;
            vis[nx][ny] = 1;
            q.push({nx, ny});
            cnt ++;
        }
    }
    // for (int i = 1; i <= n; i ++) 
    //     for (int j = 1; j <= n; j ++) 
    //         cout << (vis[i][j] ? "1" : "0") << " \n"[j == n];
    return cnt;
}
int main(void) {
    cin >> n >> m;
    for (int i = 1; i <= n; i ++) {
        cin >> grid[i];
        grid[i] = ' ' + grid[i];
    } 
    while (m --) {
        int x, y;
        cin >> x >> y;
        cout << bfs(x, y) << '\n';
    }
    return 0;
}