LeetCode 345. Reverse Vowels of a String (Easy)

反转字符串中的所有元音字母。

原始问题

https://leetcode.com/problems/reverse-vowels-of-a-string/

Write a function that takes a string as input and reverse only the vowels of a string.

Example 1:
Given s = “hello”, return “holle”.

Example 2:
Given s = “leetcode”, return “leotcede”.

Note:
The vowels does not include the letter “y”.

解题思路

双指针，一个left从头部开始找，另一个right从尾部开始找，若left及right均为元音，交换二者。截止条件为left >= right。

AC代码

C语言

#define checkVowel(c) (c=='a'||c=='e'||c=='i'||c=='o'||c=='u'||c=='A'||c=='E'||c=='I'||c=='O'||c=='U')

char * reverseVowels(char* s) {
    char * left, *right;
    char tmpc;

    // Initialize pointer
    left = s;
    right = s;

    while (*right != '\0') {
        right++;
    }

    while (1) {
        while (!checkVowel(*left)) {
            left++;
        }
        
        while (!checkVowel(*right)) {
            right--;
        }
        
        if (left < right) {
            tmpc = *left;
            *left = *right;
            *right = tmpc;
            left++;
            right--;
        } else {
            return s;
        }
    }

    return s;
}

这里判断是否为元音字母使用了宏定义，以此提高运行效率。

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LeetCode 344. Reverse String (Easy)