Leetcode 345. Reverse Vowels of a String

Leetcode 345. Reverse Vowels of a String

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

Example 1:Input: “hello”
Output: “holle”
Example 2:Input: “leetcode”
Output: “leotcede”

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

题目大意：将一个字符串内的元音字母进行反转。
注意：原因字母不包括y，且包括大小写。

解题思路：采用头尾双指针，如果两个指针值都为元音字母则进行交换，否则往中间移动。时间复杂度为O(n).

代码1：

class Solution {
public:
    bool isVowels(char c){
        return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u' || c == 'A' || c == 'E' || c == 'I' || c == 'O' || c == 'U';
    }
    
    string reverseVowels(string s) {
        int i = 0, j = s.size() - 1;
        while(i < j)
        {
            if(isVowels(s[i]) && isVowels(s[j]))
                swap(s[i++], s[j--]);
            else if(isVowels(s[i]))
                j--;
            else
                i++;
        }
        return s;
    }
};

代码2：

class Solution {
public:
      string reverseVowels(string s) {
        int i = 0, j = s.size() - 1;
        while(i < j)
        {
            i = s.find_first_of("aeiouAEIOU", i);
            j = s.find_last_of("aeiouAEIOU", j);
            if(i < j)
                swap(s[i++], s[j--]);
        }
        return s;
    }
};