[leetcode] Combination Sum

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, … , a_k) must be in non-descending order. (ie, a₁ ≤ a₂ ≤ … ≤ a_k).
• 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:
  void generateCombination(vector<vector<int> > &ret, const vector<int> &candidates, vector<int> &temp, int temp_target, int index)
  {
    for(int i=index; i<candidates.size(); i++)
    {
      if(temp_target == 0)
        ret.push_back(temp);

      if(candidates[i] <= temp_target)
      {
        temp.push_back(candidates[i]);
        generateCombination(ret, candidates, temp, temp_target-candidates[i], i);
        temp.pop_back();
      }
      else
        return;
    }
  }
  vector<vector<int> > combinationSum(vector<int> &candidates, int target)
  {
    vector<vector<int> > ret;
    vector<int> temp;
    sort(candidates.begin(), candidates.end());
    generateCombination(ret, candidates, temp, target, 0);

    return ret;
  }
};