四面楚歌

#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
const int N = 1010;
int n,m,dx[] = {1,0,0,-1},dy[] = {0,-1,1,0},ans = 0;
char g[N][N];
void dfs(int x,int y){
    for(int i = 0;i <= 3;i++){//走四个方向
        int xi = x+dx[i],yi = dy[i] + y;
        if(xi >= 0 && xi <= n + 1 && yi <= m + 1 && yi >= 0 && g[xi][yi] !='1'){
            if(g[xi][yi]=='0')ans++;
            g[xi][yi] = '1';
            dfs(xi,yi);
        }
    }
}
int main()
{
    cin>>n>>m;
    for (int i = 1; i <= n; i ++ )
        for (int j = 1; j <= m; j ++ )
            cin>>g[i][j];

    dfs(0,0);//从墙边开始枚举
    cout<<ans;
    return 0;
}