POJ 1321 棋盘问题

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <cstdlib>
 6 #include <algorithm>
 7 #include <stack>
 8 #include <set>
 9 #include <map>
10 #include <queue>
11 #include <ctime>
12 #define LL long long
13 #define INF 0x3f3f3f3f
14 #define pii pair<int,int>
15 
16 using namespace std;
17 const int maxn = 10;
18 char table[maxn][maxn];
19 int n,k,sum;
20 bool vis[maxn];
21 void dfs(int cur,int cnt){
22     if(cnt == k){
23         ++sum;
24         return;
25     }
26     if(cur >= n || n-cur < k-cnt) return;
27     for(int i = 0; i < n; ++i){
28         if(vis[i]||table[cur][i] == ‘.‘) continue;
29         vis[i] = true;
30         dfs(cur+1,cnt+1);
31         vis[i] = false;
32     }
33     dfs(cur+1,cnt);
34 }
35 int main(){
36     while(scanf("%d %d",&n,&k),~n || ~k){
37         memset(table,‘\0‘,sizeof(table));
38         memset(vis,false,sizeof(vis));
39         for(int i = sum = 0; i < n; ++i)
40             scanf("%s",table[i]);
41         dfs(0,0);
42         printf("%d\n",sum);
43     }
44     return 0;
45 }