動機

LIS的進化版

Problem

Given an integer array nums, find a contiguous non-empty subarray within the array that has the largest product, and return the product.

It is guaranteed that the answer will fit in a 32-bit integer.

A subarray is a contiguous subsequence of the array.

 

Example 1:

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

Example 2:

Input: nums = [-2,0,-1]Output: 0Explanation: 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.

Sol

與原本的LIS很像，但有負數!! 所以要記錄最小的數

class Solution:
    def maxProduct(self, nums: List[int]) -> int:
        ret = a = b = nums[0]
        for n in nums[1:]:
            a,b = max(a*n,b*n,n), min(a*n,b*n,n)
            ret = max(ret, a, b)
        return ret