Method permute

java/0046-permutations.java:6–10

(int[] nums)

class Solution {

    public List<List<Integer>> permute(int[] nums) {
        List<List<Integer>> ans = new ArrayList<>();
        function(ans, nums, 0);
        return ans;
    }

    public void function(List<List<Integer>> ans, int[] arr, int start) {
        if (start == arr.length) {