Target Sum Expression

Given a list of numbers and a target value, insert + or - operators or choose not to insert any operators between numbers to calculate the target value. Find out all possible combinations. Input A list of integers nums with length n, where 1 <= n <= 20. A target integer target, where -1000 <= target <= 1000. Output The number of possible combinations to reach the target value. Example 1 Input: nums = [1, 1, 1, 1, 1], target = 3 Output: 5 Explanation: There are 5 ways to get 3: - +1-1+1+1+1=3 - -1+1+1+1+1=3 - +1+1-1+1+1=3 - +1+1+1-1+1=3 - +1+1+1+1-1=3 Example 2 Input: nums = [1], target = 1 Output: 1 Note Each element is treated independently and can be followed by a + or - sign, or no sign at all. Find all possible combinations that lead to the target value. Example Input 5 1 1 1 1 1 3