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.
  • 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]
]
 1 public class Solution {
 2     public List<List<Integer>> combinationSum(int[] candidates, int target) {
 3         List<List<Integer>> result = new ArrayList<>();
 4         if (candidates == null || candidates.length == 0) {
 5             return result;
 6         }
 7         List<Integer> list = new ArrayList<>();
 8         Arrays.sort(candidates);
 9         helper(candidates, result, list, 0, target);
10         return result;
11     }
12     
13     private void helper(int[] candidates, List<List<Integer>> result, List<Integer> list, int index, int target) {
14         if (target == 0) {
15             result.add(new ArrayList<Integer>(list));
16         }
17         for (int i = index; i < candidates.length; i++) {
18             if (candidates[i] > target) {
19                 break;
20             }
21             if (i != index && candidates[i] == candidates[i - 1]) {
22                 continue;
23             }
24             list.add(candidates[i]);
25             helper(candidates, result, list, i, target - candidates[i]);
26             list.remove(list.size() - 1);
27         }
28     }
29 }

 

posted @ 2016-09-12 08:51  YuriFLAG  阅读(118)  评论(0)    收藏  举报