普-疑问……

蒟蒻，大佬勿喷%%

#include<bits/stdc++.h>
using namespace std;

#define int long long
const int N = 1e2+5;
int dx[5] = {0,0,1,-1},
    dy[5] = {1,-1,0,0};
int n,m;
bool vis[N][N],b[N][N],c;

void dfs(int x,int y)
{
    if(x<1 or y<1 or x>n or y>m or b[x][y] or c or vis[x][y]) return;
    if(x == n and y == m)
    {
        c = 1;
        return;
    }
    vis[x][y] = 1;
    for(int i = 0;i<4;i++)
    {
        dfs(x+dx[i],y+dy[i]);
    }
    //vis[x][y] = 0;
}

signed main()
{
    ios::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    cin>>n>>m;
    for(int i = 1;i<=n;i++)
        for(int j = 1;j<=m;j++)
        {
            char c;
            cin>>c;
            if(c == '#') b[i][j] = 1;
        }
    dfs(1,1);
    if(c) cout<<"Yes"<<endl;
    else cout<<"No"<<endl;
    return 0;
}

这道题为什么不用回溯qwq，回溯就t了，不回溯就过了