Leetcode128: Combination Sum

Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.

The same repeated number may be chosen from C unlimited number of times.

Note:

• All numbers (including target) will be positive integers.
• Elements in a combination (a1, a2, … , ak) must be in non-descending order. (ie, a1 ≤ a2 ≤ … ≤ ak).
• The solution set must not contain duplicate combinations.

For example, given candidate set 

2,3,6,7

 and target 

7

, 

A solution set is: 

[7]

[2, 2, 3]

class Solution {
public:
    vector<vector<int>> res;
    int sum(vector<int> tmp)
    {
        int sum=0;
        for(int i = 0; i < tmp.size(); i++)
            sum+=tmp[i];
        return sum;
    }
    void dfs(vector<int>& candidates, vector<int>& tmp, int target, int l)
    {
        int n = sum(tmp);
        if(n == target)
        {
            res.push_back(tmp);
            return;
        }
        else if(n > target)
            return;
        else
        {
            for(int i = l; i < candidates.size(); i++)
            {
                tmp.push_back(candidates[i]);
                dfs(candidates, tmp, target, i);
                tmp.pop_back();
            }
        }
    }
    vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
        vector<int> tmp;
        sort(candidates.begin(), candidates.end());
        dfs(candidates, tmp, target, 0);
        return res;
    }
};