[leetcode]90. Subsets II数组子集(有重)

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

Note: The solution set must not contain duplicate subsets.

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

题意：

是的[leetcode]78. Subsets数组子集 follow up 

这题强调给定数组可以有重复元素

思路：

需要先对给定数组排序，以便去重

代码：

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