1567. Maximum Length of Subarray With Positive Product

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].

Example 4:

Input: nums = [-1,2]
Output: 1

Example 5:

Input: nums = [1,2,3,5,-6,4,0,10]
Output: 4

Constraints:

• 1 <= nums.length <= 10^5
• -10^9 <= nums[i] <= 10^9

# @lc code=start
using LeetCode

function get_max_len(nums::Vector{Int})::Int
    pos_pre = neg_pre = max_ans = 0
    for num in nums
        if num == 0
            pos_pre = neg_pre = 0
        elseif num > 0
            pos_pre = pos_pre + 1
            neg_pre = neg_pre != 0 ? neg_pre + 1 : 0
        else
            neg_tmp = neg_pre
            neg_pre = pos_pre != 0 ? pos_pre + 1 : 1
            pos_pre = neg_tmp != 0 ? neg_tmp + 1 : 0
        end
        max_ans = max(max_ans, pos_pre)
    end
    return max_ans
end

# @lc code=end

get_max_len (generic function with 1 method)

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