[POJ1321]棋盘问题

[POJ1321]棋盘问题

#include<iostream>
#include<string.h>
#include<stdio.h>
using namespace std;
int n,m,cnt;
bool column[10];
char f[10][10];
void dfs(int step,int t)
{
    if(t>m)
    {
        ++cnt;
        return;
    }
    if(step>n)return;
    for(int i=1;i<=n;++i)
        if(!column[i] && f[step][i]=='#')
        {
            column[i]=1;
            dfs(step+1,t+1);
            column[i]=0;
        }
    dfs(step+1,t);
}
int main()
{
//    freopen("board.in","r",stdin);
//    freopen("board.out","w",stdout);
    while(~scanf("%d%d",&n,&m))
    {
        if(n==-1 && m==-1) break;
        if(m>n)
        {
            printf("0");
            continue;
        }
        for(int i=1;i<=n;++i)
            for(int j=1;j<=n;++j)
                cin>>f[i][j];
        cnt=0;
        memset(column,0,sizeof(column));
        dfs(1,1);
        printf("%d\n",cnt);
    }
}
/*
2 1
#.
.#
4 4
...#
..#.
.#..
#...
-1 -1
*/