八皇后 DFS

【转】http://blog.youkuaiyun.com/zxy_snow/article/details/5949706

 

//八皇后
#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <memory.h>
using namespace std;
const int n = 8;
int map[10][10],visit[10][10];
int num,Q;
int find(int x,int y)
{
    int sum = 0;
    for(int i=1; i<=n; i++)  //判断对应的列是否已有皇后
    {
        sum += visit[i][y];
    }
    int b = y;
    int a = x;
    for(int i=1; i<=n; i++)
        for(int k=1; k<=n; k++)
        {
			if( abs( i-x ) == abs( k-y ))
				sum += visit[i][k];
		}
    return sum == 0 ? 1 : 0 ;
}
void DFS(int d)
{
    if( Q == 8 )
    {
        num++;
        return;
    }
    for(int i=1; i<=n; i++)
    {
        if( !visit[d][i] && find(d,i) )
        {
            visit[d][i] = 1;
            Q++;
            DFS( d+1 );
            visit[d][i] = 0;
            Q--;
        }
    }
    
}
int main()
{
    num = 0; Q = 0;
    memset(map,0,sizeof(map));
    memset(visit,0,sizeof(visit));
    DFS(1);
    cout << num << endl;
    system("pause");
    return 0;
}