【leetcode46】 permutation 全排列

“The Linux philosophy is “Laugh in the face of danger”.Oops.Wrong One. “Do it yourself”. Yes, that”s it.”
Linux的哲学就是“在危险面前放声大笑”，呵呵，不是这句，应该是“一切靠自己，自力更生”才对。

`java
/**

• 全排列
  */
  public class leetcode46 {
  public List<List> permute (int[] nums) {

  List<List<Integer>> res = new ArrayList<>();
  helper(res, nums, 0);
  return res;
  

  }

  private void helper (List<List> res, int[] nums, int pos) {

  if (pos == nums.length) {
      List<Integer> list = new ArrayList<>();
      for (int t : nums) {
          list.add(t);
      }
      res.add(list);
  }
  for (int i = pos; i < nums.length; i++) {
      swap(nums, pos, i);
      helper(res, nums, pos + 1);
      swap(nums, pos, i);
  }
  

  }

  private void swap (int[] nums, int i, int j) {

  int temp = nums[i];
  nums[i] = nums[j];
  nums[j] = temp;
  

  }
  }

`**