HDU 1312 Red and Black（经典DFS）

嗯...

 

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1312

一道很经典的dfs，设置上下左右四个方向，读入时记下起点，然后跑dfs即可...最后答案加上起点的1，无需回溯！！

 

AC代码：

 1 #include<cstdio>
 2 #include<iostream>
 3 #include<cstring>
 4 
 5 using namespace std;
 6 
 7 int dir[4][2] = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}};
 8 
 9 int n, m, ans;
10 bool flag[25][25];
11 char g[25][25];
12 
13 inline void dfs(int x, int y){
14     for(int i = 0; i < 4; i++){
15         int nx = x + dir[i][0];
16         int ny = y + dir[i][1];
17         if(nx <= m && ny <= n && nx > 0 && ny > 0 && !flag[nx][ny] && g[nx][ny] == '.'){
18             ans++;
19             flag[nx][ny] = 1;
20             dfs(nx, ny);
21         }
22     }
23 }
24 
25 int main(){
26     while(~scanf("%d%d", &n, &m) && n != 0 && m != 0){
27         int x, y;
28         memset(flag, 0, sizeof(flag));
29         for(int i = 1; i <= m; i++){
30             for(int j = 1; j <= n; j++){
31                 cin >> g[i][j];
32                 if(g[i][j] == '@'){ x = i; y = j;}
33             }
34         }
35         ans = 0;
36         flag[x][y] = 1;
37         dfs(x, y);
38         printf("%d\n", ans + 1);
39     }
40     return 0;
41 }
42     

AC代码