Find the Minimum and Maximum Number of Nodes

lcpy gen -n 2058   # by problem number
lcpy gen -s find_the_minimum_and_maximum_number_of_nodes_between_critical_points   # by problem name

Input: head = [3,1]
Output: [-1,-1]

Input: head = [5,3,1,2,5,1,2]
Output: [1,3]

Input: head = [1,3,2,2,3,2,2,2,7]
Output: [3,3]

from leetcode_py import ListNode


class Solution:
    # Time: O(n)
    # Space: O(1)
    def nodes_between_critical_points(self, head: ListNode[int] | None) -> list[int]:
        first = prev = 0
        min_gap = 10**6
        count = 0
        pos = 1
        if head is None or head.next is None or head.next.next is None:
            return [-1, -1]
        prev_val = head.val
        curr = head.next
        while curr.next is not None:
            next_val = curr.next.val
            if (curr.val > prev_val and curr.val > next_val) or (
                curr.val < prev_val and curr.val < next_val
            ):
                if count == 0:
                    first = pos
                else:
                    min_gap = min(min_gap, pos - prev)
                prev = pos
                count += 1
            prev_val = curr.val
            curr = curr.next
            pos += 1
        if count < 2:
            return [-1, -1]
        return [min_gap, prev - first]