题解 | #没有重复项数字的全排列#

import java.util.*;

public class Solution {
    public ArrayList<ArrayList<Integer>> permute(int[] num) {
        ArrayList<ArrayList<Integer>> ret=new ArrayList<ArrayList<Integer>>();
        int len=num.length;
        dfs(num,ret,0);
          Collections.sort(ret, new Comparator<ArrayList<Integer>>() {
            @Override
            public int compare(ArrayList<Integer> o1, ArrayList<Integer> o2) {
                StringBuilder oo1 = new StringBuilder();
                StringBuilder oo2 = new StringBuilder();
                o1.stream().forEach(x -> oo1.append(x));
                o2.stream().forEach(x -> oo2.append(x));
                 return o1.toString().compareTo(o2.toString());
            }
        });
        
        return ret;
    }

    public void dfs(int[] nums,ArrayList<ArrayList<Integer>> ret,int k){
        if(k==nums.length){
            ArrayList<Integer> list=new ArrayList<>();
            for(int i=0;i<nums.length;i++){
                list.add(nums[i]);
            }
            ret.add(list);
            return;
        }
        for(int i=k;i<nums.length;i++){
            swap(nums,k,i);
            dfs(nums,ret,k+1);
            swap(nums,k,i);
        }
    }
    public void swap(int[]nums,int i,int j){
        int temp=nums[i];
        nums[i]=nums[j];
        nums[j]=temp;
    }
}