[LeetCode] 345. Reverse Vowels of a String

轉自LeetCode

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".

<Solution>

思考如下

• 用一個 HashSet 來查目前的字母是不是母音

• 用兩個指標，分別從兩端開始找母音，找到就交換

code 如下

Java

	class Solution {
	public String reverseVowels(String s) {
	final HashSet<Character> vowels = new HashSet<>();
	int front = 0, end = s.length()-1;
	char[] ans = s.toCharArray();
	char tmp;
	vowels.add('a');
	vowels.add('e');
	vowels.add('i');
	vowels.add('o');
	vowels.add('u');
	vowels.add('A');
	vowels.add('E');
	vowels.add('I');
	vowels.add('O');
	vowels.add('U');
	while(front < end) {
	while(front < end && !vowels.contains(ans[front])) {
	++front;
	}
	while(front < end && !vowels.contains(ans[end])) {
	--end;
	}
	if(front < end) {
	tmp = ans[front];
	ans[front++] = ans[end];
	ans[end--] = tmp;
	}
	}
	return new String(ans);
	}
	}

view raw reverseVowelsInTheString.java hosted with ❤ by GitHub

C++

	class Solution {
	public:
	string reverseVowels(string s) {
	unordered_set<char> table;
	table.insert('a');
	table.insert('e');
	table.insert('i');
	table.insert('o');
	table.insert('u');
	table.insert('A');
	table.insert('E');
	table.insert('I');
	table.insert('O');
	table.insert('U');
	int left = 0, right = s.length()-1;
	while(left < right) {
	while(left < right && table.find(s[left]) == table.end()) {
	++left;
	}
	while(left < right && table.find(s[right]) == table.end()) {
	--right;
	}
	if(left < right) {
	swap(s[left++], s[right--]);
	}
	}
	return s;
	}
	};

view raw reverseVowelsInTheString.cpp hosted with ❤ by GitHub