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152. Maximum Product Subarray

Medium

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.

Example 1:

Input: nums = [2,3,-2,4]
Output: 6
Explanation: [2,3] has the largest product 6.

Example 2:

Input: nums = [-2,0,-1]
Output: 0
Explanation: The result cannot be 2, because [-2,-1] is not a subarray.

Constraints:

  • 1 <= nums.length <= 2 * 104
  • -10 <= nums[i] <= 10
  • The product of any prefix or suffix of nums is guaranteed to fit in a 32-bit integer.

Solution

class Solution:
    def maxProduct(self, nums: List[int]) -> int:
        res = nums[0]
        currMin = nums[0]  # for negative numbers
        currMax = nums[0]

        for i in range(1, len(nums)):
            mini = currMin * nums[i]
            maxi = currMax * nums[i]
            currMin = min(nums[i], mini, maxi)
            currMax = max(nums[i], mini, maxi)
            res = max(res, currMax)

        return res