题解 | #没有重复项数字的全排列#

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param num int整型一维数组
     * @return int整型ArrayList<ArrayList<>>
     */
    public static ArrayList<ArrayList<Integer>> permute (int[] num) {
        // write code here
        ArrayList<ArrayList<Integer>> result = new ArrayList<>();
        boolean[] selected = new boolean[num.length];
        makeList(num, new ArrayList<>(),selected,result);
        return result;
    }

    public static void makeList(int[] num, ArrayList<Integer> curList, boolean[] selected,ArrayList<ArrayList<Integer>> result){
        ArrayList<Integer> localList = new ArrayList<>(curList);

        if(localList.size() == num.length){
            result.add(localList);
            return;
        }

        for(int i=0;i<num.length;i++){
            if(!selected[i]){
                //以数组中某一个数开始递归
                localList.add(num[i]);
                selected[i] = true;
                makeList(num,localList,selected,result);
                selected[i] = false;
                //移出这个递归的数，下次循环，再选另一个数开始递归
                localList.remove(localList.size()-1);
            }
        }
    }
}