[LeetCode] 39. Combination Sum

回溯法即可

void cbhelp(vector<vector<int>> &res,vector<int> &v,int target,int i,vector<int> recp){if(target<0) return;else if(target==0){res.push_back(recp);return;}for(unsigned int k=i;k<v.size();++k){recp.push_back(v[k]);cbhelp(res,v,target-v[k],k,recp);recp.pop_back();if(target-v[k]<0) return;}}vector<vector<int>> combinationSum(vector<int>& v, int target){sort(v.begin(),v.end());vector<vector<int>> res;vector<int> recp;cbhelp(res,v,target,0,recp);return res;}