1567. Maximum Length of Subarray With Positive Product

Description

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

 

Solutions

Solution: Dynamic Programming

• Time complexity: O(n)
• Space complexity: O(1)

 

JavaScript

/**
 * @param {number[]} nums
 * @return {number}
 */
const getMaxLen = function (nums) {
  let result = (positive = negative = 0);

  for (const num of nums) {
    if (num === 0) positive = negative = 0;
    else if (num > 0) {
      positive += 1;
      negative && (negative += 1);
    } else {
      const current = positive;

      positive = negative ? negative + 1 : 0;
      negative = current + 1;
    }
    result = Math.max(result, positive);
  }
  return result;
};