题解！！！| 入门？？？

打卡题解

#include <bits/stdc++.h>
using namespace std;
int w,h,a,b;
char mp[1005][1005];
int maxn = 1;
int vis[1005][1005];
int dir1[10] = {0,0,-1,1};
int dir2[10] = {1,-1,0,0};
void dfs(int x, int y){
    vis[x][y] = 1;
    for(int i = 0 ; i < 4; i++){
       int nx = x + dir1[i];
       int ny = y + dir2[i];
        if(nx >= 1 && ny >= 1 && nx <= h && ny <= w && mp[nx][ny] == '.' && vis[nx][ny] == 0){  //判断可不可以走，1.有没有越界 2.能不能走 3.走没走过
            maxn++;
            dfs(nx,ny);  //递归
        }
    }
}
int main(){
    cin >> w >> h;
    for(int i = 1; i <= h; i++){
        for(int j = 1; j <= w; j++){
            cin >> mp[i][j];
            if(mp[i][j] == '@'){   //如果遇到 @ 先把它变成 . 
                a = i;
                b = j;
                mp[i][j] = '.';
            }
        }
    }
    dfs(a,b);
    cout << maxn;
    
    return 0;
}