FindLongestBitonicSubarrayInAList.py

from random import randrange


def findBitonicSublist(A):
 
    n = len(A)
    if n == 0:
        return
 
    end_index = 0
    max_len = 1
    i = 0
 
    while i + 1 < n:
 
        # check for the longest bitonic subarray starting at `A[i]`
 
        # reset length to 1
        length = 1
 
        # run till sequence is increasing
        while i + 1 < n and A[i] < A[i + 1]:
            i = i + 1
            length = length + 1
 
        # run till sequence is decreasing
        while i + 1 < n and A[i] > A[i + 1]:
            i = i + 1
            length = length + 1
 
        # run till sequence is equal
        while i + 1 < n and A[i] == A[i + 1]:
            i = i + 1
 
        # update longest bitonic subarray if required
        if length > max_len:
            max_len = length
            end_index = i
 
    # print the longest bitonic subarray
    print("The length of the longest bitonic subarray is", max_len)
    print("The longest bitonic subarray is", A[end_index - max_len + 1: end_index + 1])
 
 
if __name__ == '__main__':
 
    A = [3, 5, 8, 4, 5, 9, 10, 8, 5, 3, 4]
    findBitonicSublist(A)