反转字符串的元音字符：算法之美

2024-01-13 04:52:09

题意分析

给定一个字符串s，你的任务是仅反转字符串中的所有元音字母，并返回结果字符串。元音字母包括'a'、'e'、'i'、'o'、'u'，且可能以大小写两种形式出现。

解题思路

方法一：双指针

双指针法是一种经典的字符串处理算法，它使用两个指针分别指向字符串的两端，然后从两端向中间移动，比较字符是否相等。如果相等，则交换两个字符，否则继续移动指针。

def reverse_vowels(s):
  """
  Reverses the vowels in a string.

  Args:
    s: The string to reverse the vowels in.

  Returns:
    The string with the vowels reversed.
  """

  # Initialize the left and right pointers.
  left, right = 0, len(s) - 1

  # Create a set of vowels.
  vowels = set("aeiouAEIOU")

  # While the left pointer is less than or equal to the right pointer, continue.
  while left <= right:
    # If the character at the left pointer is a vowel, and the character at the right pointer is a vowel, swap the characters.
    if s[left] in vowels and s[right] in vowels:
      s = s[:left] + s[right] + s[left+1:right] + s[left] + s[right+1:]
      # Move the left and right pointers inward.
      left += 1
      right -= 1
    # If the character at the left pointer is not a vowel, move the left pointer inward.
    elif s[left] not in vowels:
      left += 1
    # If the character at the right pointer is not a vowel, move the right pointer inward.
    elif s[right] not in vowels:
      right -= 1

  # Return the reversed string.
  return s

方法二：使用正则表达式

正则表达式是一种强大的工具，它可以用来查找和替换字符串中的文本。我们可以使用正则表达式来查找字符串中的所有元音字母，然后用其对应的相反元音字母替换它们。

import re

def reverse_vowels(s):
  """
  Reverses the vowels in a string.

  Args:
    s: The string to reverse the vowels in.

  Returns:
    The string with the vowels reversed.
  """

  # Create a regular expression that matches all vowels.
  vowel_regex = re.compile("[aeiouAEIOU]")

  # Find all the vowels in the string.
  vowels = vowel_regex.findall(s)

  # Reverse the list of vowels.
  vowels.reverse()

  # Replace the vowels in the string with the reversed list of vowels.
  reversed_s = vowel_regex.sub(lambda m: vowels.pop(0), s)

  # Return the reversed string.
  return reversed_s