Combination Sum

Medium

Question

Given a list of unique positive integers and a target, find all unique combinations in the list where its sum is equal to the target.

Input: nums = [2, 3, 5], target = 8

Output: [[2, 2, 2, 2], [2, 3, 3], [3, 5]]

There are 3 unique combinations that sum up to 8.

Input: nums = [2, 4, 6, 8], target = 8

Output: [[2, 2, 2, 2], [2, 2, 4], [2, 6], [4, 4], [8]]

There are 5 unique combinations that sum up to 8.

Input: nums = [2, 4, 6, 8], target = 9

Output: []

There are no combinations that sum up to 9.

What are some questions you'd ask an interviewer?

How many unique combinations are there when nums = [2, 3, 7] and target = 7?