leetcode -- Subsets II

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

Note:

• Elements in a subset must be in non-descending order.
• The solution set must not contain duplicate subsets.

 For example,

If S = [1,2,2], a solution is:

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

[解题思路]
本题与Subsets唯一区别在于输入会有重复元素，这是面试时需要注意的，尽可能考虑所有输入情况
代码与上一题只在25-27有区别，当发现重复元素时则跳过

public class Solution {
    public ArrayList<ArrayList<Integer>> subsetsWithDup(int[] num) {
        // Start typing your Java solution below
        // DO NOT write main() function
        Arrays.sort(num);
        ArrayList<ArrayList<Integer>> result = new ArrayList<ArrayList<Integer>>();
        ArrayList<Integer> output = new ArrayList<Integer>();
        generate(result, output, 0, num, num.length);
        return result;
    }
    
     public void generate(ArrayList<ArrayList<Integer>> result, ArrayList<Integer> output,
                    int depth, int[] S, int len){
        result.add(output);
        if(depth == len){
            return;
        }
        
        for(int i = depth; i < len; i++){
            ArrayList<Integer> tmp = new ArrayList<Integer>();
            tmp.addAll(output);
            tmp.add(S[i]);
            generate(result, tmp, i + 1, S, len);
            
25             while(i + 1 < len && S[i] == S[i+1]){
26                 i++;
27             }
        }
    }
}