Leetcode 377. Combination Sum IV

medium Apple interview question

Given an array of distinct integers nums and a target integer target, return the number of possible combinations that add up to target.

The answer is guaranteed to fit in a 32-bit integer.

Example 1:

Input: nums = [1,2,3], target = 4
Output: 7
Explanation:
The possible combination ways are:
(1, 1, 1, 1)
(1, 1, 2)
(1, 2, 1)
(1, 3)
(2, 1, 1)
(2, 2)
(3, 1)
Note that different sequences are counted as different combinations.
Example 2:

Input: nums = [9], target = 3
Output: 0

Idea

Solution