hdu 2553 N皇后问题 (经典DFS)

#include<stdio.h>
#include<stdlib.h>
int hang[11],n,sum;
int ans[11];
bool judge(int num)
{
for(int i = 1 ; i < num ; i ++)
if(hang[num] == hang[i] || abs(hang[i] - hang[num]) == num - i)//判断列和对角线
return 0;
return 1;
}
void dfs(int num)
{
for(int i = 1 ; i <= n ; i ++)
{
hang[num] = i;
if(judge(num))
{
if(num == n) sum ++;
else  dfs(num + 1);
}
}
}
int main()
{
int i,m;
for(i = 1 ; i < 11 ; i ++)//打表
{
sum = 0;
n = i;
dfs(1);
ans[i] = sum;
}
while(scanf("%d",&m) && m)
printf("%d\n",ans[m]);
return 0;
}