algorithms/algorithms/string/reverse_string.py at main · mitchricker/algorithms · GitHub

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"""

Reverse String

Reverse a string using four different approaches: recursive, iterative,

pythonic (using reversed), and ultra-pythonic (using slicing).

Reference: https://en.wikipedia.org/wiki/String_(computer_science)#Reversal

Complexity:

Time: O(n) for all approaches

Space: O(n) for all approaches, O(log n) stack for recursive

"""

from __future__ import annotations

def recursive(text: str) -> str:

"""Reverse a string using a recursive divide-and-conquer approach.

Args:

text: The string to reverse.

Returns:

The reversed string.

Examples:

>>> recursive("hello there")

'ereht olleh'

"""

length = len(text)

if length < 2:

return text

return recursive(text[length // 2 :]) + recursive(text[: length // 2])

def iterative(text: str) -> str:

"""Reverse a string using iterative character swapping.

Args:

text: The string to reverse.

Returns:

The reversed string.

Examples:

>>> iterative("hello there")

'ereht olleh'

"""

characters = list(text)

left, right = 0, len(text) - 1

while left < right:

characters[left], characters[right] = (

characters[right],

characters[left],

)

left += 1

right -= 1

return "".join(characters)

def pythonic(text: str) -> str:

"""Reverse a string using the built-in reversed function.

Args:

text: The string to reverse.

Returns:

The reversed string.

Examples:

>>> pythonic("hello there")

'ereht olleh'

"""

characters = list(reversed(text))

return "".join(characters)

def ultra_pythonic(text: str) -> str:

"""Reverse a string using slice notation.

Args:

text: The string to reverse.

Returns:

The reversed string.

Examples:

>>> ultra_pythonic("hello there")

'ereht olleh'

"""

return text[::-1]

algorithms/algorithms/string/reverse_string.py at main · mitchricker/algorithms · GitHub

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