LeetCode——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] 

原题链接：https://oj.leetcode.com/problems/combination-sum/

<span style="font-size:18px;">public class CombinationSum {
	private List<Integer> list = new  ArrayList<Integer>();
	private List<List<Integer>> result = new ArrayList<List<Integer>>();
	public List<List<Integer>> combinationSum(int[] candidates, int target) {
		if(candidates.length == 0)
			return result;
		Arrays.sort(candidates);
		dfs(candidates,target,0);
		return result;
	}
	public void dfs(int[] candidates,int target,int index){
		if(target < 0)
			return;
		if(target == 0){
			result.add(new ArrayList<Integer>(list));
			return;
		}
		for(int i=index;i<candidates.length;i++){
			if(i>0 && candidates[i] == candidates[i-1])
				continue;
			list.add(candidates[i]);
			dfs(candidates,target-candidates[i],i);
			list.remove(list.size()-1);
		}
	}
}
</span>