AcWing 1112. 迷宫（连通性）

题目链接：点击这里

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>

using namespace std;
const int N = 110;

int dx[] = {-1, 1, 0, 0};
int dy[] = {0 , 0, -1, 1};

char g[N][N];
bool st[N][N];
int n, ax, ay, bx, by;

bool dfs(int x, int y)
{
    if(g[x][y] == '#')  return false;
    
    if(x == bx && y == by)  return true;
    
    st[x][y] = true;
    for(int i = 0; i < 4; ++i)
    {
        int a = x + dx[i], b = y + dy[i];
        if(a < 0 || a >= n || b < 0 || b >= n)  continue;
        if(st[a][b])    continue;
        
        if(dfs(a, b))   return true;
    }
    
    return false;
}


int main()
{
    int T;
    scanf("%d", &T);
    
    while(T--)
    {
        memset(st, false, sizeof st);
        
        scanf("%d", &n);
        for(int i = 0; i < n; ++i)  scanf("%s", g[i]);
        
        scanf("%d%d%d%d", &ax, &ay, &bx, &by);
        
        if(dfs(ax, ay))   puts("YES");
        else    puts("NO");
    }
    
    return 0;
}