Combination Sum IV

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

The test cases are generated so that the answer can fit in a 32-bit integer.

Input Format:

First Parameter: Length of the array n

Second Parameter: Array of n distinct integers nums

Third Parameter: Target integer target

Output Format:

Return a single integer which is equal to the number of ways to make up the target

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

Constraints:

• n = nums.length
• 1 <= n <= 200
• 1 <= nums[i] <= 1000
• All the elements of nums are unique.
• 1 <= target <= 1000
• Expected Time Complexity - O(n*target)
• Expected Space Complexity - O(target)