POJ 1321 棋盘问题 dfs回溯

#include<iostream>
#include<cstdio>
#include<string>
#include<cstring>
using namespace std;
int  map[10][10];
int n,k;
int ans;
bool judge(int x,int y)
{
for(int i=x-1;i>=0;i--)
{
if(map[i][y]==2)return 0;
}

for(int i=y-1;i>=0;i--)
{
if(map[x][i]==2)return 0;
}
return 1;
}

void dfs(int u,int Sum)
{
if(u>n*n)return ;
if(Sum==k)
{
ans++;
return ;
}

int r=u/n;
int c=u%n;
if(map[r][c]==1&&judge(r,c))
{
map[r][c]=2;
dfs(u+1,Sum+1);
map[r][c]=1;
}
dfs(u+1,Sum);
}

int main()
{
char ch;
int i,j;
while(~scanf("%d%d",&n,&k))
{
if(n==-1&&k==-1)
break;
getchar();
memset(map,0,sizeof(map));
for(i=0;i<n;i++)
for(j=0;j<n;j++)
{
cin>>ch;

if(ch=='#')map[i][j]=1;
}
ans=0;
dfs(0,0);
printf("%d\n",ans);
}
return 0;
}