# Find bitonic point in given bitonic sequence in Python

Suppose we have a bitonic sequence, we have to find the Bitonic Point in it. As we know a Bitonic Sequence is a sequence of numbers which is first strictly increasing then after a certain point it is strictly decreasing. This point is bitonic point. For only increasing or only decreasing sequences, bitonic points are not available.

So, if the input is like [7, 8, 9, 12, 10, 6, 3, 2], then the output will be 12

To solve this, we will follow these steps −

• define a function binary_search(array, l, r)
• if l <= r, then −
• m := (l + r) / /2
• if array[m - 1] < array[m] and array[m] > array[m + 1], then −
• return m
• if array[m] < array[m + 1], then −
• return binary_search(array, m + 1, r)
• Otherwise
• return binary_search(array, l, m - 1)
• return -1

## Example

Let us see the following implementation to get better understanding −

Live Demo

def binary_search(array, l, r):
if (l <= r):
m = (l + r) // 2;
if (array[m - 1] < array[m] and array[m] > array[m + 1]):
return m;
if (array[m] < array[m + 1]):
return binary_search(array, m + 1,r);
else:
return binary_search(array, l, m - 1);
return -1;
array = [7, 8, 9, 12, 10, 6, 3, 2]
n = len(array);
index = binary_search(array, 1, n-2);
if (index != -1):
print(array[index]);

## Input

[7, 8, 9, 12, 10, 6, 3, 2]

## Output

12

Updated on: 28-Aug-2020

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