hdoj2553(N皇后问题)

Problem : 2553 ( N皇后问题 )     Judge Status : Accepted
RunId : 2619754    Language : G++    Author : huwenbiao
Code Render Status : Rendered By HDOJ G++ Code Render Version 0.01 Beta

/***************************************************************\
 *Author:Hu Wenbiao
 *Created Time: Sat 17 Jul 2010 10:35:51 AM CST
 *File Name: a.cpp
 *Description:回溯
\***************************************************************/
//*========================*Head File*========================*\\

#include<iostream>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
/*----------------------*Global Variable*----------------------*/
int X[11],N,sum;
//*=======================*Main Program*=======================*//
using namespace std;

bool place(int k){
    for(int j=1;j<k;++j){
        if(X[j]==X[k]||abs(k-j)==abs(X[k]-X[j]))
          return false;
    }
    return true;
}

void backtrack(int k){
    if(k>N)
      sum++;
    else{
        for(int i=1;i<=N;++i){
              X[k]=i;
              if(place(k)){
                  backtrack(k+1);
              }
        }
    }
}
int main(){
    //freopen("input","r",stdin);
    int ans[11];

    for(N=1;N<=10;++N){
        sum=0;
        backtrack(1);
        ans[N]=sum;
    }
    while(scanf("%d",&N)!=-1&&N){
        printf("%d\n",ans[N]);
    }
}