leetcode—— 39——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>> combinationSum(vector<int>& candidates, int target)
{
vector<vector<int>> result;
vector<int> path;
sort(candidates.begin(),candidates.end());
helper(candidates,0,target,path,result);
return result;

}
void helper(vector<int> &nums,int pos,int target,vector<int>& path,vector<vector<int>> & result)
{
if(0==target)
{
result.push_back(path);
return ;

}
if(target < 0) return ;
for(int i=pos;i<nums.size();i++)
{
path.push_back(nums[i]);
helper(nums,i,target-nums[i],path,result);
path.pop_back();

}
}
};