[LeetCode]345. Reverse Vowels of a String

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Problem

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

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Example 1:

Input: "hello"
Output: "holle"
Example 2:

Input: "leetcode"
Output: "leotcede"

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

Solution

Analysis

翻转字符串中的元音字母. 首先,我们需要记录元音字母都有哪些, 然后双指针遍历字符串,判断当前字符是否属于元音字母,找到之后交换位置,继续遍历.

Code

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class Solution {
public:
    string reverseVowels(string s) {
        set<char> vowels{'a','e','i','o','u', 'A','E','I', 'O','U'};
        int size = s.size(), l = 0, r = size - 1;
        
        while (l < r){
            while (l < size && vowels.count(s[l]) == 0) l++;
            while (r > l && vowels.count(s[r]) == 0) r--;
            
            if (l >= size || r <= l)
                break;
            else{
                swap(s[l++], s[r--]);
            }
        }
        return s;
    }
};
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