LeetCode Combination Sum

题意

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.
给定一个数组和一个目标值，求出所有加起来的和等于这个目标值的组合

解法

可以用DFS来解，每次选取一个新的值时只能在数组里往后找而不能往前找，这样就避免了重复。

class Solution
{
	vector<vector<int>>	ans;

public:
	vector<vector<int>> combinationSum(vector<int>& candidates, int target)
	{
		ans.clear();
		vector<int>	temp;
		dfs(0,0,candidates,target,temp);
		return	ans;
	}

	void	dfs(int k,int sum,vector<int>& candidates, int target,vector<int> temp)
	{
		if(sum == target)
			ans.push_back(temp);

		for(int i = k;i < candidates.size();i ++)
			if(sum + candidates[i] <= target)
			{
				temp.push_back(candidates[i]);
				dfs(i,sum + candidates[i],candidates,target,temp);
				temp.pop_back();
			}
	}
};