题:https://leetcode.com/problems/reverse-vowels-of-a-string/description/
题目
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
反转字符串中的元音字符
思路
使用双指针 一个指针从头向尾遍历,一个指针从尾到头遍历 ,指向待反转的两个元音字符。然后交换元素。
class Solution {
static Set<Character> vowels = new HashSet<>(Arrays.asList('a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U'));
public String reverseVowels(String s) {
int lp = 0,rp = s.length()-1;
char[] chs = s.toCharArray();
while(lp<rp){
while(lp<rp && !vowels.contains(chs[lp]))
lp++;
while(lp<rp && !vowels.contains(chs[rp]))
rp--;
if(lp<rp){
char tc = chs[lp];
chs[lp] = chs[rp];
chs[rp] = tc;
lp++;
rp--;
}
}
return String.valueOf(chs);
}
}
重新 生成 chars,性能要差些。
class Solution {
static Set<Character> vowels = new HashSet<>(Arrays.asList('a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U'));
public String reverseVowels(String s) {
int i = 0, j = s.length() - 1;
char[] result = new char[s.length()];
while (i <= j) {
char ci = s.charAt(i);
char cj = s.charAt(j);
if (!vowels.contains(ci)) {
result[i++] = ci;
} else if (!vowels.contains(cj)) {
result[j--] = cj;
} else {
result[i++] = cj;
result[j--] = ci;
}
}
return new String(result);
}
}