View Code of Problem 450

#include <iostream>
#include<cstdio>
#include<cstring>
using namespace std;
char chess[8][8];
bool vis[8];
int chess_size;
int n,k;
int ans;
void dfs(int f,int num){
    if(f >= n || num == k){
        if(num == k){
            ans ++;
           // cout << ans << endl;
        }
        return;
    }
    for(int j = f+1;j < n;j ++)
    {
        //if(n-1-j >= k-num){     //保证层数够
            for(int k = 0;k < n;k ++){
                //cout << "j=" << j << "k=" << k << endl;
                if(chess[j][k] == '#' && !vis[k]){
                    //cout << "j=" << j  << " "<< "k=" << k << endl;
                    vis[k] = true;
                    dfs(j,num+1);
                    vis[k] = false;
                }
            }
       // }
    }
}
int main()
{
    int i ,j;
    while(scanf("%d %d",&n,&k)!=EOF)
    {
        getchar();
        if(n == -1&&k == -1)
            break;
        for( i = 0;i < n;i ++)
        {
            for( j = 0;j < n;j ++){
                scanf("%c",&chess[i][j]);
            }
            getchar();
        }
        memset(vis,false,sizeof(vis));
        ans = 0;
        for(i = 0;i <= n-k;i ++)//第一层的所有可能
        {
            for(j = 0;j < n;j ++)
            {
                if(chess[i][j] == '#')
                {
                    //cout << "i=" << i << "j=" << j << endl;
                    vis[j] = true;
                    dfs(i,1);                      //j代表层数，0代表个数
                    vis[j] = false;
                }
            }
        }
        cout << ans << endl;
    }
    return 0;
}