Example 1:
Input: nums = [-2, 1, -3, 4, -1, 2, 1, -5, 4]
Output: 6
Explanation: The subarray [4, -1, 2, 1] has the largest sum 6.
Example 2:
Input: nums = [1]
Output: 1
Explanation: The subarray [1] has the largest sum 1.
Example 3:
Input: nums = [5, 4, -1, 7, 8]
Output: 23
Explanation: The subarray [5, 4, -1, 7, 8] has the largest sum 23.