leetcode回溯法欣赏——配合前文套路教学效果更佳

Leetcode 回溯法欣赏，助你发现其中套路（部分内容引自评论区）

Subsets : https://leetcode.com/problems/subsets/

public List<List<Integer>> subsets(int[] nums) {
    List<List<Integer>> list = new ArrayList<>();
    Arrays.sort(nums);
    backtrack(list, new ArrayList<>(), nums, 0);
    return list;
}

private void backtrack(List<List<Integer>> list , List<Integer> tempList, int [] nums, int start){
    list.add(new ArrayList<>(tempList));
    for(int i = start; i < nums.length; i++){
        tempList.add(nums[i]);
        backtrack(list, tempList, nums, i + 1);
        tempList.remove(tempList.size() - 1);
    }
}

Subsets II (contains duplicates) : https://leetcode.com/problems/subsets-ii/

public List<List<Integer>> subsetsWithDup(int[] nums) {
    List<List<Integer>> list = new ArrayList<