90. Subsets II

题目：

Given a collection of integers that might contain duplicates, nums, return all possible subsets.

Note: The solution set must not contain duplicate subsets.

For example,
If nums = [1,2,2], a solution is:

[
  [2],
  [1],
  [1,2,2],
  [2,2],
  [1,2],
  []
]

链接：https://leetcode.com/problems/subsets-ii/#/description

4/22/2017

算法班

37%, 3ms

与第78题只有一句话的区别，就是第21行去重

public class Solution {

    public List<List<Integer>> subsetsWithDup(int[] nums) {
        // write your code here
        List<List<Integer>> ret = new ArrayList<>();
        
        Arrays.sort(nums);
        
        helper(ret, new ArrayList<Integer>(), nums, 0);
        
        return ret;
    }
    
    private void helper(List<List<Integer>> ret,
                        ArrayList<Integer> subset,
                        int[] nums,
                        int startIndex) {
        ret.add(new ArrayList<Integer>(subset));
        
        for (int i = startIndex; i < nums.length; i++) {
            if (i > startIndex && nums[i] == nums[i - 1]) continue;
            subset.add(nums[i]);
            helper(ret, subset, nums, i + 1);
            subset.remove(subset.size() - 1);
        }
    }    
}

别人iterative的解释

https://discuss.leetcode.com/topic/4661/c-solution-and-explanation

更多讨论：

https://discuss.leetcode.com/category/98/subsets-ii