LeetCode345. 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".

这道题的关键在于如何同时交换两个元音字母。我们这里采取的方法是分别找到左边和右边的元音字母然后交换。

另外，我们这里使用了用数组来“哈希”字母的trick。

class Solution {
public:
	string reverseVowels(string s) {
		vector<int> v(256, 0);
		v['a'] = 1;
		v['e'] = 1;
		v['i'] = 1;
		v['o'] = 1;
		v['u'] = 1;

		v['A'] = 1;
		v['E'] = 1;
		v['I'] = 1;
		v['O'] = 1;
		v['U'] = 1;

		int left = 0, right = int(s.size() - 1);
		while (left < right) {
			while (left < right && !v[s[left]]) left++;
			while (left < right && !v[s[right]]) right--;
			swap(s[left], s[right]);
			left++; right--;
		}
		return s;
	}
};