Leetcode Combination Sum II

Combination Sum II

  Total Accepted: 3894  Total Submissions: 16733 My Submissions

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] 

标准递归回溯法可以搞定，防止重复，使用set容器。

class Solution {
public:
    vector<vector<int> > combinationSum2(vector<int> &num, int target) 
	{
		sort(num.begin(), num.end());
		vector<int> tmp;
		set<vector<int> > rs;
		
		comb(rs, tmp, num, target);
		return vector<vector<int> >(rs.begin(), rs.end());
	}

	void comb(set<vector<int> > &rs, vector<int> &tmp, 
		vector<int> &num, int tar, int index=0)
	{
		if (!tmp.empty() && tar == 0) rs.insert(tmp);

		for (int i = index; i < num.size(); i++)
		{
			if (tar < num[i]) return;

			tmp.push_back(num[i]);
			comb(rs, tmp, num, tar-num[i], i+1);
			tmp.pop_back();
		}
	}
};