Problem: Maximum Subarray

Given an integer array, nums, find the contiguous subarray that has the largest sum and return its sum.

Note: A subarray is a contiguous part of an array that contains at least one number.

Constraints:

• $1 \leq$ nums.length $\leq 10^3$

• $-10^4 \leq$ nums[i] $\leq 10^4$