LeetCode之字符串处理题java

344. Reverse String

Write a function that takes a string as input and returns the string reversed.

Example:
Given s = "hello", return "olleh".

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public class Solution {
    public String reverseString(String s) {
        if(s==null)
            return "";
        char c[] = s.toCharArray();
        int len = s.length();
        int i=0;
        int j=len-1;
        while(i<j){
            char tmp = c[i];
            c[i] = c[j];
            c[j] = tmp;
            ++i;
            --j;
        }
        return new String(c);
    }
}

345. Reverse Vowels of a String

Total Accepted: 4116 Total Submissions: 11368 Difficulty: Easy

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".

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采用快排的partition函数来对字符串进行翻转

public class Solution {
    public  String reverseVowels(String s) {
        if(s==null){
            return "";
        }
        char[] c = s.toCharArray();
        int left = 0;
        int right = c.length-1;
        while(left<right){
            while(left<right&&!isVowel(c[left])){
                ++left;
            }
            while(left<right&&!isVowel(c[right])){
                --right;
            }
            char tmp = c[left];
            c[left] = c[right];
            c[right] = tmp;
            ++left;
            --right;
        }
        return new String(c);
    }　　//检查一个字符是否是元音字符
    public boolean isVowel(char c){
        if(c==‘a‘||c==‘e‘||c==‘i‘||c==‘o‘||c==‘u‘||c==‘A‘||c==‘E‘||c==‘I‘||c==‘O‘||c==‘U‘)
            return true;
        else
            return false;
    }
}