46_Permutations.java

classSolution {
publicList<List<Integer>> permute(int[] nums) {
if (nums == null || nums.length == 0) {
returnCollections.emptyList();
 }

List<List<Integer>> result = newArrayList<>();
helper(nums, result, newArrayList<>());

returnresult;
 }

privatevoidhelper(int[] nums, List<List<Integer>> result, List<Integer> temp) {
if (temp.size() == nums.length) {
result.add(newArrayList<>(temp));
return;
 }

for (inti = 0; i < nums.length; i++) {
if (temp.contains(nums[i])) {
continue;
 }

temp.add(nums[i]);
helper(nums, result, temp);
temp.remove(temp.size() - 1);
 }
 }
}