leetcode344 Reverse String Java

Description

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

Example:
Given s = “hello”, return “olleh”.

解法1

第一时间想起了stack，于是写了如下代码，可是提示Time Limit Exceeded~~~

public String reverseString(String s) {        String res = "";        Stack<Character> stack = new Stack<>();        char[] ch = s.toCharArray();        int count = 0;        for(char c : ch) {            count++;            stack.push(c);        }        for(int i=0; i<count;i++) {            res += stack.pop();        }        return res;    }

解法2

直接用StringBuffer的reverse()方法。

public String reverseString1(String s) {        return new StringBuffer(s).reverse().toString();    }

解法3

调换s的第一位和最后一位，第二位和倒数第二位……..

public String reverseString2(String s) {        char[] word = s.toCharArray();        int i = 0, j = word.length -1;        while(i<j) {            char tmp = word[i];            word[i] = word[j];            word[j] = tmp;            i++;            j--;        }        return new String(word);    }

第五六七行 word[i]和word[j]对换位置可以替换为：

word[i] = (char) (word[i] ^ word[j]);word[j] = (char) (word[i] ^ word[j]);word[i] = (char) (word[i] ^ word[j]);