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60 lines
1.6 KiB
Python
60 lines
1.6 KiB
Python
"""
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Pure Python implementation of a binary search algorithm.
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For doctests run following command:
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python3 -m doctest -v simple_binary_search.py
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For manual testing run:
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python3 simple_binary_search.py
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"""
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from __future__ import annotations
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def binary_search(a_list: list[int], item: int) -> bool:
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"""
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>>> test_list = [0, 1, 2, 8, 13, 17, 19, 32, 42]
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>>> binary_search(test_list, 3)
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False
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>>> binary_search(test_list, 13)
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True
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>>> binary_search([4, 4, 5, 6, 7], 4)
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True
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>>> binary_search([4, 4, 5, 6, 7], -10)
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False
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>>> binary_search([-18, 2], -18)
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True
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>>> binary_search([5], 5)
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True
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>>> binary_search(['a', 'c', 'd'], 'c')
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True
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>>> binary_search(['a', 'c', 'd'], 'f')
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False
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>>> binary_search([], 1)
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False
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>>> binary_search([-.1, .1 , .8], .1)
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True
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>>> binary_search(range(-5000, 5000, 10), 80)
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True
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>>> binary_search(range(-5000, 5000, 10), 1255)
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False
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>>> binary_search(range(0, 10000, 5), 2)
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False
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"""
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if len(a_list) == 0:
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return False
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midpoint = len(a_list) // 2
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if a_list[midpoint] == item:
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return True
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if item < a_list[midpoint]:
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return binary_search(a_list[:midpoint], item)
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else:
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return binary_search(a_list[midpoint + 1 :], item)
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if __name__ == "__main__":
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user_input = input("Enter numbers separated by comma:\n").strip()
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sequence = [int(item.strip()) for item in user_input.split(",")]
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target = int(input("Enter the number to be found in the list:\n").strip())
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not_str = "" if binary_search(sequence, target) else "not "
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print(f"{target} was {not_str}found in {sequence}")
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