LeetCode345.md

title: LeetCode 345. Reverse Vowels of a String (Easy) weburl: LeetCode_345 toc: true mathjax: false fancybox: false tags: [Online Judge] categories: 算法之美 date: 2016-10-25 20:36:38

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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。

相关题目

LeetCode 344. Reverse String (Easy)