python/TangDou/AcWing/Dfs/1112_bfs_bool.cpp

#include <bits/stdc++.h>
using namespace std;
struct Node {
    int x;
    int y;
    int step;
};
const int N = 110;
int dx[] = {-1, 0, 1, 0};
int dy[] = {0, 1, 0, -1};
char g[N][N];
bool st[N][N];
int n;
int xa, ya, xb, yb; // 不能使用x1,y1这样的变量名，可能是万能头中有重复声明
bool flag;
void bfs() {
    flag = false;
    if (g[xa][ya] == '#') return;
    if (g[xb][yb] == '#') return;
    memset(st, 0, sizeof st);

    if (xa == xb && ya == yb) {
        flag = true;
        return;
    }

    queue<Node> q;
    q.push({xa, ya, 0});
    st[xa][ya] = true;

    while (q.size()) {
        auto t = q.front();
        q.pop();
        for (int i = 0; i < 4; i++) {
            int x = t.x + dx[i], y = t.y + dy[i];
            if (x < 0 || x >= n || y < 0 || y >= n) continue;
            if (st[x][y]) continue;
            if (g[x][y] == '#') continue;
            if (x == xb && y == yb) {
                flag = true;
                return;
            }
            q.push({x, y, t.step + 1});
            st[x][y] = true;
        }
    }
}
int main() {
    int T;
    cin >> T;
    while (T--) {
        cin >> n;
        for (int i = 0; i < n; i++) cin >> g[i];

        cin >> xa >> ya >> xb >> yb;
        bfs();
        if (flag)
            cout << "YES" << endl;
        else
            cout << "NO" << endl;
    }
    return 0;
}