Combination Sum IV
You are 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.
Example 1:
Input: nums = [3,1,2], target = 4
Output: 7Explanation: The possible combination ways are:
(1, 1, 1, 1)
(1, 1, 2)
(1, 2, 1)
(1, 3)
(2, 1, 1)
(2, 2)
(3, 1)
Example 2:
Input: nums = [1], target = 3
Output: 1Constraints:
1 <= nums.length <= 2001 <= nums[i], target <= 1000- All the elements of
numsare unique.
Follow up: What if negative numbers are allowed in the given array? How does it change the problem? What limitation we need to add to the question to allow negative numbers?