LeetCode Problem : Combination Sum II

Problem

Given a collection of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.

Each number in C may only be used once in the combination.

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 10,1,2,7,6,1,5 and target 8, 
A solution set is: 
[1, 7] 
[1, 2, 5] 
[2, 6] 
[1, 1, 6] 

Code

void DFS_cs2(int pos,int k,int target,const vector<int> &num,
vector<int> &out,vector<vector<int> > &result)
{
    if(target == 0){
        result.push_back(vector<int>(out.begin(),out.begin() + pos));
        return;
    }
    if(target < 0)
        return;
    if(pos == out.size())
        out.resize(2*pos + 1);
    for(int i = k;i < num.size();++i){ 
        if(i != 0 && i != k && num[i] == num[i - 1])
            continue;
        out[pos] = num[i];
        DFS_cs2(pos + 1,i + 1,target - num[i],num,out,result);
    }
}
vector<vector<int> > combinationSum2(vector<int> &num, int target) {
    // Note: The Solution object is instantiated only once and is reused by each test case.
    vector<vector<int> >result;
    vector<int> out;
    sort(num.begin(),num.end());
    DFS_cs2(0,0,target,num,out,result);
    return result;
}