fjnu 1151 Queens

Queens

Time Limit: 1 Seconds     Memory Limit: 32768 K Total Submit:155     Accepted:98

Description You are to find the number of different combinations of placement of N queens on the NxN board. Every queen should NOT attack another (i.e. there should be no two figures sharing the same vertical, horizontal or diagonal. Input Number 1<=N<10. NOTE:Input is terminated when N=0. Output The number of valid combinations. Sample Input 8 Sample Output 92

 KEY:经典的N皇后问题……回溯吧……

 

Source:

#include<iostream>
using namespace std;

int sum;
int x[11];
int n;

int place(int k)
...{
    for(int j=1;j<k;j++)
        if( (abs(k-j)==abs(x[j]-x[k]))||(x[j]==x[k]) ) return 0;
    return 1;
}

void fun(int t)
...{
    if(t>n) sum++;
    else
    ...{
        for(int i=1;i<=n;i++)
        ...{
            x[t]=i;
            if(place(t)) fun(t+1);
        }
    }
}

int main()
...{
    while(cin>>n&&n!=0)
    ...{
        sum=0;
        for(int i=1;i<=n;i++)
            x[i]=0;
        fun(1);
        cout<<sum<<endl;
    }
    return 0;
}