Java for LeetCode 039 Combination Sum

標籤：

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]

解題思路：

首先說明下題目Bug，實際測試中C中元素是不會重複的，因此降低了不少難度，最簡單的實現方法，DFS演算法，JAVA實現如下：

static public List<List<Integer>> combinationSum(int[] candidates,int target) {List<List<Integer>> list = new ArrayList<List<Integer>>();Arrays.sort(candidates);dfs(list, candidates, 0, target, 0);return list;}static List<Integer> list2 = new ArrayList<Integer>();static void dfs(List<List<Integer>> list, int[] array, int result,int target, int depth) {if (result == target) {list.add(new ArrayList<Integer>(list2));return;}else if (depth >= array.length || result > target)return;for (int i = 0; i <= target / array[depth]; i++) {for (int j = 0; j < i; j++)list2.add(array[depth]);dfs(list, array, result + array[depth] * i, target, depth+1);for (int j = 0; j < i; j++)list2.remove(list2.size() - 1);}}

 

Java for LeetCode 039 Combination Sum