POJ 1321 棋盘问题

解题思路:DFS

#include <iostream>
using namespace std;
char chess[8][9];
int n, m;
inline bool IsOk(int i, int j)
{
    int k;bool istrue=true;
    for(k=0;k<i && istrue;k++)
        if(chess[k][j]=='*')istrue = false;
    return istrue;
}
int DFS(int layer, int k)
{
    if(k==0)return 1;
    if(n-layer+1<k)return 0;
    int i,d=0;
    for(i=0;i<n;i++)
    {
        if(chess[layer-1][i]=='#'&&IsOk(layer-1, i))
        {
            chess[layer-1][i]='*';
            d += DFS(layer+1,k-1);
            chess[layer-1][i]='#';
        }
    }
    d += DFS(layer+1, k);
    return d;
}

int main()
{
    int i, ans;
    while(scanf("%d %d", &n, &m) && !(n==-1&&m==-1))
    {
        for(ans = i = 0;i < n;i++)scanf("%s",chess[i]);
        ans = DFS(1, m);
        printf("%d\n", ans);
    }
    return 0;
}