Leetcode: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 > combinationSum(vector &candidates, int target) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        vector > v_results;
                if(candidates.empty() )
                        return v_results;  
                sort(candidates.begin(),candidates.end() );
                vector result;
                helper(candidates,0,target,result,v_results);
                return v_results;
    }
     void helper(vector& candidates,int pos,int target,vector& result,vector >& v_results)
        {   
                if(target==0)
                {   
                        v_results.push_back(result);
                        return;
                }   
                if(pos>=candidates.size() )
                        return;
                int num = target/candidates[pos];
                for(int i=0;i<=num;++i)
                {   
                        for(int j=0;j

这题是完全背包，DP求总方案数很容易，但求路径没想到DP复杂度的，想到的还是记录路径然后再递归，所以干脆直接递归。