package leetcode;

import java.util.ArrayList;
import java.util.List;

public class demo_46 {
    public List<List<Integer>> permute(int[] nums) {
        List<List<Integer>> list=new ArrayList<List<Integer>>();
        //设置数组记录当前循环中该数字是否被访问
        int[] visited=new int[nums.length];
        for(int i=0;i<nums.length;i++) {
            visited[i]=0;
        }
        backtrack(list,nums,new ArrayList<Integer>(),visited);
        System.out.println(list);
        return list;
    }
    
    public void backtrack(List<List<Integer>> list,int[] nums,List<Integer> alist,int[] visited) {
        if(alist.size()==nums.length) {
            list.add(new ArrayList<Integer>(alist));
        }
        else {
            for(int j=0;j<nums.length;j++) {
                //若当前数字已被访问则继续循环
                if(visited[j]==1) {continue;}
                alist.add(nums[j]);
                visited[j]=1;
                backtrack(list, nums,alist,visited);
                alist.remove(alist.size()-1);
                visited[j]=0;
            }
        }
    }
    public static void main(String[] args) { 
        // TODO Auto-generated method stub
        demo_46 d46 = new demo_46();
        int[] nums= {1,2,3};
        d46.permute(nums);
    }

}