Problem

Given a string, you need to reverse the order of characters in each word within a sentence while still preserving whitespace and initial word order.

Example 1:

Input: "Let's take LeetCode contest"Output: "s'teL ekat edoCteeL tsetnoc"Note: In the string, each word is separated by single space and there will not be any extra space in the string.

Solution

class Solution {    public String reverseWords(String s) {        if (s == null || s.length() == 0) return s;        String[] strs = s.split(" ");        StringBuilder sb = new StringBuilder();        for (String str: strs) {            str = reverse(str);            sb.append(str).append(" ");        }        return sb.toString().trim();    }    private String reverse(String str) {        StringBuilder sb = new StringBuilder();        for (int i = str.length()-1; i >= 0; i--) {            sb.append(str.charAt(i));        }        return sb.toString();    }}

StringBuilder for everything

class Solution {    public String reverseWords(String s) {        String[] strs = s.split(" ");        StringBuilder sb = new StringBuilder();        for (String str: strs) {            str = new StringBuilder(str).reverse().toString();            sb.append(str+" ");        }        return sb.toString().trim();    }}