八皇后之回溯算法

package problem.回溯;

public class EightQueue {

    public static int max = 8,sum = 0;
    public static int[] queen = new int[max]; //存储列元素值
    
    //皇后元素形式：（i,queue[i])
    public void displayQueen(){
        for(int i=0;i<queen.length;i++)
        {
            System.out.print("("+i+","+queen[i]+")");
        }
        System.out.println();
        sum++;
    }
    
    public boolean check(int n){
        for(int i=0;i<n;i++){
            //判断元素不在同一列和对角线上
            if(queen[i]==queen[n] || Math.abs(queen[i]-queen[n])==(n-i)){
                return false;
            }
        }
        return true;
    }
    
    public void put(int n){
        for(int i=0;i<max;i++){
            queen[n] = i; //把该列上的每个元素尝试一下
            if(check(n)){
                if(n==max-1) 
                    displayQueen();
                else 
                    put(n+1);
            }
        }
    }
    
    public static void main(String[] args) {
        EightQueue eq = new EightQueue();
        eq.put(0);
        System.out.println("sum="+sum);
    }
}