40. Combination Sum II

class Solution 
{
public:
    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) 
    {
        vector<vector<int>> res;
        vector<int> cur;
        sort(candidates.begin(),candidates.end());
        helper(res,candidates,cur,target,0);
        return res;
    }
    
    void helper(vector<vector<int>> &res,vector<int> &candidates,vector<int> &cur,int target,int index)
    {
        if(target<0)
            return;
        if(target==0)
        {
            res.push_back(cur);
            return;
        }
        int sz=candidates.size();
        for(int i=index;i<sz;i++)
        {
            cur.push_back(candidates[i]);
            helper(res,candidates,cur,target-candidates[i],i+1);
            cur.pop_back();
            while(i+1!=sz&&candidates[i+1]==candidates[i])
                i++;
        }
    }
};

要注意排除重复元素，并且在下一次迭代时，从下一个元素的位置开始