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71 lines
1.8 KiB
Python
71 lines
1.8 KiB
Python
"""
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Pure Python implementation of the jump search algorithm.
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This algorithm iterates through a sorted collection with a step of n^(1/2),
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until the element compared is bigger than the one searched.
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It will then perform a linear search until it matches the wanted number.
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If not found, it returns -1.
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https://en.wikipedia.org/wiki/Jump_search
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"""
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import math
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from collections.abc import Sequence
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from typing import Any, Protocol, TypeVar
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class Comparable(Protocol):
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def __lt__(self, other: Any, /) -> bool: ...
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T = TypeVar("T", bound=Comparable)
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def jump_search(arr: Sequence[T], item: T) -> int:
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"""
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Python implementation of the jump search algorithm.
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Return the index if the `item` is found, otherwise return -1.
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Examples:
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>>> jump_search([0, 1, 2, 3, 4, 5], 3)
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3
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>>> jump_search([-5, -2, -1], -1)
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2
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>>> jump_search([0, 5, 10, 20], 8)
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-1
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>>> jump_search([0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610], 55)
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10
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>>> jump_search(["aa", "bb", "cc", "dd", "ee", "ff"], "ee")
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4
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"""
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arr_size = len(arr)
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block_size = int(math.sqrt(arr_size))
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prev = 0
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step = block_size
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while arr[min(step, arr_size) - 1] < item:
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prev = step
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step += block_size
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if prev >= arr_size:
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return -1
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while arr[prev] < item:
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prev += 1
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if prev == min(step, arr_size):
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return -1
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if arr[prev] == item:
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return prev
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return -1
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if __name__ == "__main__":
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user_input = input("Enter numbers separated by a comma:\n").strip()
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array = [int(item) for item in user_input.split(",")]
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x = int(input("Enter the number to be searched:\n"))
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res = jump_search(array, x)
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if res == -1:
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print("Number not found!")
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else:
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print(f"Number {x} is at index {res}")
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