迷宫

https://www.acwing.com/problem/content/1114/

#include<bits/stdc++.h>
using namespace std;
const int N = 150;
char g[N][N];
bool st[N][N];
int n;
int sx, sy, ex, ey;
int dx[] = { -1, 1, 0, 0 }, dy[] = { 0, 0, -1, 1 };

void dfs(int x,int y)
{
    st[x][y] = true;

    bool success = false;
    for (int i = 0; i < 4; i++)
    {
        int nx = x + dx[i], ny = y + dy[i];
        if (nx >= 1 && nx <= n&&ny >= 1 && ny <= n&&st[nx][ny] == false&&g[nx][ny]=='.')
        {
            success = true;
            dfs(nx, ny);
        }
    }
    if (!success) return;
}

int main()
{
    int t;
    cin >> t;
    while (t--)
    {
        cin >> n;
        for (int i = 1; i <= n; i++)
        {
            for (int j = 1; j <= n; j++)
            {
                cin >> g[i][j];
            }
        }
        cin >> sx >> sy >> ex >> ey;
        sx++, sy++, ex++, ey++;

        memset(st, false, sizeof st);
        dfs(sx,sy);
        if (g[sx][sy] == '#' || g[ex][ey] == '#') puts("NO");
        else
        {
            if (st[ex][ey]) puts("YES");
            else puts("NO");
        }
    }
    return 0;
}