Combination Sum

Return every unique combination of candidates that adds up to target. Each number can be used many times. Order doesn’t matter: [2, 2, 3] and [3, 2, 2] are the same. Any order of answers is fine.

Examples

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]]