Given an integer array nums, find the subarray with the largest sum, and return its sum.
A subarray is a contiguous non-empty sequence of elements within an array.
1 <= nums.length <= 10^5-10^4 <= nums[i] <= 10^4nums = [-2,1,-3,4,-1,2,1,-5,4]6nums = [1]1nums = [5,4,-1,7,8]23