[Lintcode]191. Maximum Product Subarray/[Leetcode]152. Maximum Product Subarray

191. Maximum Product Subarray/152. Maximum Product Subarray

• 本题难度: Medium
• Topic: Dynamic Programming

Description

Given an integer array nums, find the contiguous subarray within an array (containing at least one number) which has the largest product.

Example 1:

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

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

我的代码

def maxProduct(self, nums):
    # write your code here
    lmax = nums[0]
    lmin = nums[0]
    res = nums[0]
    for num in nums[1:]:
        if num<0:
            lmin, lmax = lmax, lmin
        lmin = min(num*lmin,num)
        lmax = max(num*lmax,num)
        if lmax>res:
            res = lmax
    return res

思路
[2,3, -2, 4, -1 ,2,-3]
2, 6, -2, 4, 48 , 96, 32
2, 3, -12, -48, -4, -8, 288
第一行为连续到这一点的子数列最大值。
第二行为连续到这一点的子数列最小值。

• 时间复杂度 O(n)