Given an integer array nums, find a subarray that has the largest product, and return the product.
The test cases are generated so that the answer will fit in a 32-bit integer.
Input: nums = [2,3,-2,4]
Output: 6
Explanation: [2,3] has the largest product 6.
Input: nums = [-2,0,-1]
Output: 0
Explanation: The result cannot be 2, because [-2,-1] is not a subarray.
1 <= nums.length <= 2 * 10^4-10 <= nums[i] <= 10