Python/searches/simple_binary_search.py

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"""
Pure Python implementation of a binary search algorithm.
For doctests run following command:
python3 -m doctest -v simple_binary_search.py
For manual testing run:
python3 simple_binary_search.py
"""
from __future__ import annotations
def binary_search(a_list: list[int], item: int) -> bool:
"""
>>> test_list = [0, 1, 2, 8, 13, 17, 19, 32, 42]
>>> print(binary_search(test_list, 3))
False
>>> print(binary_search(test_list, 13))
True
>>> print(binary_search([4, 4, 5, 6, 7], 4))
True
>>> print(binary_search([4, 4, 5, 6, 7], -10))
False
>>> print(binary_search([-18, 2], -18))
True
>>> print(binary_search([5], 5))
True
>>> print(binary_search(['a', 'c', 'd'], 'c'))
True
>>> print(binary_search(['a', 'c', 'd'], 'f'))
False
>>> print(binary_search([], 1))
False
>>> print(binary_search([.1, .4 , -.1], .1))
True
"""
if len(a_list) == 0:
return False
midpoint = len(a_list) // 2
if a_list[midpoint] == item:
return True
if item < a_list[midpoint]:
return binary_search(a_list[:midpoint], item)
else:
return binary_search(a_list[midpoint + 1 :], item)
if __name__ == "__main__":
user_input = input("Enter numbers separated by comma:\n").strip()
sequence = [int(item.strip()) for item in user_input.split(",")]
target = int(input("Enter the number to be found in the list:\n").strip())
not_str = "" if binary_search(sequence, target) else "not "
print(f"{target} was {not_str}found in {sequence}")