Combination Sum

Given a set of candidate numbers © 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:

1
2
3

[2,3,6,7] 7
[7] 
[2, 2, 3] 

这题真是基础，之前一直对此类不知所措，现在略通一二，甚喜

Code:

class Solution {
public:
    void Getcom(vector<int>&can, int target, vector<vector<int>>&result, int level, int &sumcurrent, int nsize, vector<int>&tmp)
    {
        if(sumcurrent>target)return;
        if(target==sumcurrent)
        {
            result.push_back(tmp);
            return;
        }
        for(int i=level;i<nsize;i++)
        {

                sumcurrent += can[i];
                tmp.push_back(can[i]);
                Getcom(can,target,result,i,sumcurrent,nsize,tmp);
                tmp.pop_back();
                sumcurrent -=can[i];
        }

    }
    vector<vector<int> > combinationSum(vector<int> &candidates, int target) 
    {
       vector<vector<int>> result;
       vector<int>tmp;
       int size = candidates.size();
       sort(candidates.begin(),candidates.end());
       int sumc = 0;
       Getcom(candidates,target,result,0,sumc,size,tmp);
       return result;
    }
};

DFS方便记录结果，DP方便记数