【LeetCode】90. Subsets II

1.题目描述

Given a collection of integers that might contain duplicates, nums, return all possible subsets (the power set).

给定一个可能包含重复元素的整数数组 nums，返回该数组所有可能的子集（幂集）。

Note: The solution set must not contain duplicate subsets.

说明：解集不能包含重复的子集。

Example:

Input: [1,2,2]
Output:
[
[2],
[1],
[1,2,2],
[2,2],
[1,2],
[]
]

2.Solutions

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

private static 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++){
        if(i > start && nums[i] == nums[i-1]) continue; // skip duplicates
        tempList.add(nums[i]);
        backtrack(list, tempList, nums, i + 1);
        tempList.remove(tempList.size() - 1);
    }
}

参考：78. Subsets

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