1567. Maximum Length of Subarray With Positive Product ⭐

Medium

Given an array of integers nums, find the maximum length of a subarray where the product of all its elements is positive.

A subarray of an array is a consecutive sequence of zero or more values taken out of that array.

Return the maximum length of a subarray with positive product.

Example 1:

Input: nums = [1,-2,-3,4]
Output:
 4
Explanation:
 The array nums already has a positive product of 24.

Example 2:

Input: nums = [0,1,-2,-3,-4]
Output:
 3
Explanation:
 The longest subarray with positive product is [1,-2,-3] which has a product of 6.
Notice that we cannot include 0 in the subarray since that'll make the product 0 which is not positive.

Example 3:

Input: nums = [-1,-2,-3,0,1]
Output:
 2
Explanation:
 The longest subarray with positive product is [-1,-2] or [-2,-3].

Constraints:

• 1 <= nums.length <= 105

• -109 <= nums[i] <= 109

解題

func getMaxLen(nums []int) int {
    pos, neg := make([]int, len(nums)), make([]int, len(nums))

    if nums[0] > 0 {
        pos[0] = 1
    } else if nums[0] < 0 {
        neg[0] = 1
    }

    max := pos[0]

    for i:=1; i<len(nums); i++ {
        if nums[i] > 0 {
            pos[i] = pos[i-1] + 1
            if neg[i-1] > 0 { neg[i] = 1+neg[i-1] }
        } else if nums[i] < 0 {
            neg[i] = 1+pos[i-1]
            if neg[i-1] > 0 { pos[i] = 1+neg[i-1] }
        } else {
            pos[i] = 0
            neg[i] = 0
        }

        if pos[i] > max {
            max = pos[i]
        }
    }

    return max
}