Given a collection of distinct numbers, return all possible permutations.
For example, [1,2,3] have the following permutations:
[ [1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], [3,2,1] ]Solution:
public List<List<Integer>> permute(int[] nums) { List<List<Integer>> list = new ArrayList<>(); backtrack(list, new ArrayList<>(), nums); return list; } private void backtrack(List<List<Integer>> list, List<Integer> tempList, int[] nums) { if (tempList.size() == nums.length) { list.add(new ArrayList<>(tempList)); } else { for (int i = 0; i < nums.length; i++) { if (tempList.contains(nums[i])) continue; tempList.add(nums[i]); backtrack(list, tempList, nums); tempList.remove(tempList.size() - 1); } } }