[leetcode]Subsets II

Subsets II

 

Given a collection of integers that might contain duplicates, nums, 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 nums = [1,2,2], a solution is:

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

题意：求子集 但数组中有重复元素

解题思路：记录重复元素每次插入的起点位置

class Solution {public:    vector<vector<int>> subsetsWithDup(vector<int>& nums) {        // IMPORTANT: Please reset any member data you declared, as        // the same Solution instance will be reused for each test case.        sort(nums.begin(), nums.end());        vector<vector<int> > v2;        v2.push_back(vector<int>()); //0        int n = nums.size();                int prevSize = 0; //上一次插入时集合的大小        int prevValue = nums[0]; //上一次插入时的元素值                for(int i = 0; i < n; i++){            int curSize = v2.size();            int startIdx = 0;            if(nums[i] == prevValue){                startIdx = prevSize; //新的拷贝插入起点            }                        prevSize = curSize;            for(int j = startIdx; j < curSize; j++){                vector<int> v(v2[j]);                v.push_back(nums[i]);                v2.push_back(v);            }            prevValue = nums[i];        }                return v2;            }};