视频讲解

视频连接：https://www.bilibili.com/video/BV1kN411R7Vg/

#
# 
# @param arr double浮点型一维数组 
# @return double浮点型
#
class Solution:
    def maxProduct(self , arr ):
        n = len(arr)
        # 初始化 最大 最小 dp数组
        max_dp = [1.0]*n
        min_dp = [1.0]*n
        # 赋初值
        min_dp[0] = arr[0]
        max_dp[0] = arr[0]
        total = arr[0]
        for i in range(1, n):
            if arr[i] > 0:
                # 正*正 = 正
                max_dp[i] = max(arr[i], max_dp[i-1]*arr[i])
                # 负*正= 负
                min_dp[i] = min(arr[i], min_dp[i-1]*arr[i])
            else:
                # 负*负=正
                max_dp[i] = max(arr[i], min_dp[i-1]*arr[i])
                # 正*负=负
                min_dp[i] = min(arr[i], max_dp[i-1]*arr[i])
            total = max(total, max_dp[i])
        return total