CF1365D Solve The Maze，CF官网通过，洛谷提交失败

#include <bits/stdc++.h>

using namespace std;

int cx[4] = {0, 0, 1, -1};
int cy[4] = {1, -1, 0, 0};

bool vis[55][55];
char g[55][55];

bool bfs(int n, int m, int cnt) {
    int ans = 0;
    queue<pair<int, int>> q;
    if (g[n][m] != '#') {
        q.push({n, m});
    }
    while (!q.empty()) {
        auto k = q.front();
        q.pop();
        if (g[k.first][k.second] == 'G') {
            ++ans;
        } else if (g[k.first][k.second] == 'B') {
            return false;
        }
        for (int i = 0; i < 4; ++i) {
            int x = k.first + cx[i];
            int y = k.second + cy[i];

            if (x <= 0 || x > n || y <= 0 || y > m || g[x][y] == '#') {
                continue;
            }
            if (vis[x][y]) {
                continue;
            }
            vis[x][y] = true;
            q.push({x, y});
        }
    }
    return ans == cnt;
}

void best_coder() {
    int t;
    cin >> t;
    while (t--) {
        memset(vis, false, sizeof(vis));
        memset(g, '.', sizeof(vis));
        int n, m;
        cin >> n >> m;
        int cnt = 0;
        for (int i = 1; i <= n; ++i) {
            for (int j = 1; j <= m; ++j) {
                char c;
                cin >> c;
                if (c == '.' && g[i][j] == '#') {
                    continue;
                }
                g[i][j] = c;
                if (g[i][j] == 'G') {
                    ++cnt;
                } else if (g[i][j] == 'B') {
                    for (int s = 0; s < 4; ++s) {
                        if (g[cx[s] + i][cy[s] + j] == '.') {
                            g[cx[s] + i][cy[s] + j] = '#';
                        }
                    }
                }
            }
        }

        if (bfs(n, m, cnt)) {
            cout << "Yes" << '\n';
        } else {
            cout << "No" << '\n';
        }
    }
}

void happy_coder() {

}

int main() {
    // 提升cin、cout效率
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    // 小码匠
    best_coder();

    // 最优解
    // happy_coder();

    return 0;
}