_46.java

package com.fishercoder.solutions;

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

public class _46 {

    public static class Solution1 {
        public List<List<Integer>> permute(int[] nums) {
            List<List<Integer>> result = new ArrayList();
            result.add(new ArrayList<>());
            return backtracking(nums, 0, result);
        }

        private List<List<Integer>> backtracking(int[] nums, int index, List<List<Integer>> result) {
            if (index == nums.length) {
                return result;
            }
            List<List<Integer>> newResult = new ArrayList<>();
            for (List<Integer> eachList : result) {
                for (int i = 0; i <= eachList.size(); i++) {
                    List<Integer> newList = new ArrayList<>(eachList);
                    newList.add(i, nums[index]);
                    newResult.add(newList);
                }
            }
            result = newResult;
            return backtracking(nums, index + 1, result);
        }
    }

}