345. Reverse Vowels of a String

QUESTION:

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”.

EXPLANATION:

思路就比较简单：

1.从前往后找到元音字母，从后往前找到元音字母。

2.进行交换操作。

其实就是使用了快速排序的思想。

虽然这个是个ac的解决办法，但是最后还是发现，用array进行操作的话，反而是最快的，因为array的数据结构查找是最快的。

SOLUTION:

public class Solution {
    public String reverseVowels(String s) {
        char[] chars = s.toCharArray();
        int low = 0;
        int high = chars.length - 1;
        Predicate pre = o -> {
            if(o.equals('a')||o.equals('e')||o.equals('i')||o.equals('o')||o.equals('u')||o.equals('A')||o.equals('E')||o.equals('I')||o.equals('O')||o.equals('U'))
                return true;
            return false;
        };
        while(low<=high){
            char tmp = ' ';
            while(!pre.test(chars[low])&&low<high){
                low++;
            }
            tmp = chars[low];
            while(!pre.test(chars[high])&&low<high){
                high--;
            }
            chars[low] = chars[high];
            chars[high] = tmp;
            low++;high--;
        }
        return new String(chars);
    }
}


public class Solution {
    public String reverseVowels(String s) {
        char[] chars = s.toCharArray();
        int low = 0;
        int high = chars.length - 1;
        while(low<=high){
            char tmp = ' ';
            while (!vowels[chars[low]] && low < high)
                low++;

            tmp = chars[low];
            while (!vowels[chars[high]] && low < high)
                high--;

            chars[low] = chars[high];
            chars[high] = tmp;
            low++;
            high--;
        }
        return new String(chars);
    }
    
    static boolean[] vowels = new boolean[256];
    static {
        vowels['a'] = true;
        vowels['e'] = true;
        vowels['i'] = true;
        vowels['o'] = true;
        vowels['u'] = true;
        vowels['A'] = true;
        vowels['E'] = true;
        vowels['I'] = true;
        vowels['O'] = true;
        vowels['U'] = true;
    }
}
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