Longest Peak.py

"""
   Longest Peak

   Write a function that takes in array of integers and returns the length of the longest
   peak in the array.

   A peak is defined as adjacent integers in the array that are strictly increasing until
   they reach a tip (the highest value in the peak). at which point they become strictly
   decreasing.At least three integers are required to form a peak.

   For example,the integers 1, 4, 10, 2 form a peak, but the integers 4, 0, 10 don't and
   neither do the integers 1, 2, 2, 0. Similarly,the integers 1, 2, 3 don't form a peak
   because there aren't any strictly decreasing integers after the 3.

   Sample Input
     array = [1, 2, 3, 3, 4, 0, 10, 6, 5, -1, -3, 2, 3]

   Sample Output
     6 // 0, 10, 6, 5, -1, -3

"""

# SOLUTION 1

# O(n) time | O(1) space where n is the length of the input array:
def longestPeak(array):
    longestPeakLength = 0
    i = 1
    while i < len(array) - 1:
        isPeak = array[i - 1] < array[i] and array[i] > array[i + 1]
        if not isPeak:
            i += 1
            continue
        leftIdx = i - 2
        while leftIdx >= 0 and array[leftIdx] < array[leftIdx + 1]:
            leftIdx -= 1
        rightIdx = i + 2
        while rightIdx < len(array) and array[rightIdx] < array[rightIdx - 1]:
            rightIdx += 1

        currentPeakLength = rightIdx - leftIdx - 1
        longestPeakLength = max(longestPeakLength, currentPeakLength)
        i = rightIdx
    return longestPeakLength