[LeetCode]Combination Sum II

class Solution {
	//DFS
	//sort candidates first and then DFS
	//note here how to get the unique combination: !(index != 0 && candidates[index] == candidates[index-1] && !used[index-1])
	//and the cut off trick: sumNow+candidates[index] <= target
public:
	vector<vector<int> > combinationSum2(vector<int> &candidates, int target) {
		// Start typing your C/C++ solution below
		// DO NOT write int main() function
		sort(candidates.begin(), candidates.end());
		vector<vector<int>> ans;
		vector<int> path;
		vector<bool> used(candidates.size(), false);
		combinationSum_aux(0, 0, target, path, ans, candidates, used);
		return ans;
	}

	void combinationSum_aux( int index, int sumNow, int target, vector<int>& path, vector<vector<int>>& ans, vector<int>& candidates, vector<bool>& used ) 
	{
		//throw std::exception("The method or operation is not implemented.");
		if(sumNow == target)
		{
			ans.push_back(path);
			return;
		}
		if(index >= candidates.size())
			return;

		if( !(index != 0 && candidates[index] == candidates[index-1] && !used[index-1]) && sumNow+candidates[index] <= target)
		{//cut off here is very important
			used[index] = true;
			path.push_back(candidates[index]);
			combinationSum_aux(index+1, sumNow+candidates[index], target, path, ans, candidates, used);
			path.pop_back();
			used[index] = false;
		}
		combinationSum_aux(index+1, sumNow, target, path, ans, candidates, used);
	}

};

second time

class Solution {
public:
    void combinationSumUtil(vector<int>& candidates, int target, int curIdx, vector<int>& curPath, vector<bool>& used, vector<vector<int> >& allPath)
    {
        if(target == 0)
        {
            allPath.push_back(curPath);
            return ;
        }
        if(target < 0) return;
        if(curIdx >= candidates.size()) return;        
        
        if(curIdx >= 1 && candidates[curIdx] == candidates[curIdx-1] && used[curIdx-1] == false) combinationSumUtil(candidates, target, curIdx+1, curPath, used, allPath);
        else
        {
            curPath.push_back(candidates[curIdx]);
            used[curIdx] = true;
            combinationSumUtil(candidates, target-candidates[curIdx], curIdx+1, curPath, used, allPath);
            used[curIdx] = false;
            curPath.pop_back();
            combinationSumUtil(candidates, target, curIdx+1, curPath, used, allPath);
        }
    }
    vector<vector<int> > combinationSum2(vector<int> &candidates, int target) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        sort(candidates.begin(), candidates.end());
        vector<int> curPath;
        vector<vector<int> > allPath;
        vector<bool> used(candidates.size(), false);
        combinationSumUtil(candidates, target, 0, curPath, used, allPath);
        return allPath;
    }
};