90. Subsets II (not use before so int I = start, dfs(i+1), and sort

class Solution {
    public List<List<Integer>> subsetsWithDup(int[] nums) {
        List<List<Integer>> result = new ArrayList<>();
        Arrays.sort(nums);
        dfs(nums, result, new ArrayList<>(), 0);
        return result;
    }
    private void dfs(int[] nums, List<List<Integer>> result, List<Integer> list, int start) {
        result.add(new ArrayList<>(list));
        for (int i = start; i < nums.length; i++) {
            if (i > start && nums[i] == nums[i-1]) {
                continue;
            }
            list.add(nums[i]);
            dfs(nums, result, list, i+1);
            list.remove(list.size()-1);
        }
    }
}