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  • [LeetCode] 345. Reverse Vowels of a String

    Given a string s, reverse only all the vowels in the string and return it.

    The vowels are 'a''e''i''o', and 'u', and they can appear in both cases.

    Example 1:

    Input: s = "hello"
    Output: "holle"
    

    Example 2:

    Input: s = "leetcode"
    Output: "leotcede"

    Constraints:

    • 1 <= s.length <= 3 * 105
    • s consist of printable ASCII characters.

    反转字符串中的元音字母。

    思路基本同344题。不同之处在于344题要求不能使用额外空间,但是本题非得使用额外空间才能解决,不仅需要 hashset,也需要将 input 先转成数组才能判断。同时注意这道题的 testcase 是同时包含大写字母和小写字母的。

    时间O(n)

    空间O(n) - hashset

    JavaScript实现

     1 /**
     2  * @param {string} s
     3  * @return {string}
     4  */
     5 var reverseVowels = function (s) {
     6     // corner case
     7     if (s === null || s.length === 0) return '';
     8 
     9     // normal case
    10     let res = s.split('');
    11     let vowels = new Set(['a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U']);
    12     let left = 0;
    13     let right = s.length - 1;
    14     while (left < right) {
    15         while (left < right && !vowels.has(res[left])) {
    16             left++;
    17         }
    18         while (left < right && !vowels.has(res[right])) {
    19             right--;
    20         }
    21         let temp = res[left];
    22         res[left] = res[right];
    23         res[right] = temp;
    24         left++;
    25         right--;
    26     }
    27     return res.join('');
    28 };

    Java实现

     1 class Solution {
     2     public String reverseVowels(String s) {
     3         // corner case
     4         if (s.length() == 0 || s == null) {
     5             return s;
     6         }
     7 
     8         // normal case
     9         String vowels = "aeiouAEIOU";
    10         int left = 0;
    11         int right = s.length() - 1;
    12         char[] words = s.toCharArray();
    13         while (left < right) {
    14             while (left < right && vowels.indexOf(words[left]) == -1) {
    15                 left++;
    16             }
    17             while (left < right && vowels.indexOf(words[right]) == -1) {
    18                 right--;
    19             }
    20 
    21             // swap
    22             char temp = words[left];
    23             words[left] = words[right];
    24             words[right] = temp;
    25             left++;
    26             right--;
    27         }
    28         return new String(words);
    29     }
    30 }

    相关题目

    344. Reverse String

    541. Reverse String II

    557. Reverse Words in a String III

    LeetCode 题目总结

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  • 原文地址:https://www.cnblogs.com/cnoodle/p/12424473.html
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