Combination Sum

You're given a list of distinct positive integers candidates and a positive target. Return every unique combination of candidates that adds up to target. The same candidate may be used any number of times.

Two combinations are the same if they use each number the same number of times ([2,2,3] and [3,2,2] count once). Return them in any order.

Example 1

Input: candidates = [2,3,6,7], target = 7
Output: [[2,2,3],[7]]

Example 2

Input: candidates = [2,3,5], target = 8
Output: [[2,2,2,2],[2,3,3],[3,5]]

Example 3

Input: candidates = [2], target = 1
Output: []

Constraints

• 1 ≤ len(candidates) ≤ 30
• 2 ≤ candidates[i] ≤ 40, all distinct
• 1 ≤ target ≤ 40