原题链接：https://leetcode.com/problems/reverse-string/description/
实现如下：
/**
* Created by clearbug on 2018/2/26.
*/
public class Solution {
public static void main(String[] args) {
Solution s = new Solution();
System.out.println(s.reverseString("hello"));
}
/**
* 方法二：使用双指针
*
* @param s
* @return
*/
public String reverseString(String s) {
if (s == null || s.length() < 2) {
return s;
}
char[] chars = s.toCharArray();
int i = 0, j = chars.length - 1;
while (i < j) {
char temp = chars[i];
chars[i] = chars[j];
chars[j] = temp;
i++;
j--;
}
return new String(chars);
}
/**
* 方法一：使用递归，字符串过长时会导致栈溢出
*
* Runtime Error Message: Exception in thread "main" java.lang.StackOverflowError
* @param s
* @return
*/
public String reverseString1(String s) {
if (s == null || s.length() < 2) {
return s;
}
return s.substring(s.length() - 1, s.length()) + reverseString(s.substring(0, s.length() - 1));
}
}