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
}
​