Maximum product subarray

"""
Product behaves differently than sum due to negatives.
A negative can turn a small (min) product into a large (max) one if the current element is also negative.

So at each index, track:
- max product so far from (num, num*cur_max, num*cur_min)
- min product so far

Update both using current number, and keep global max as ans.
"""

from typing import List

class Solution:
    def maxProduct(self, nums: List[int]) -> int:
        cur_max = cur_min = ans = nums[0]

        for num in nums[1:]:
            temp_max = max(num, num * cur_max, num * cur_min)
            cur_min = min(num, num * cur_max, num * cur_min)
            cur_max = temp_max

            ans = max(ans, cur_max)

        return ans