Leetcode 557. Reverse Words in a String III

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.

Code (Java):

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class Solution {     public String reverseWords(String s) {         if (s == null || s.length() < 2) {             return s;         }           int start = 0;         int end = 0;           char[] arr = s.toCharArray();           while (end < s.length()) {             while (end < s.length() && s.charAt(end) != ' ') {                 end++;             }             reverse(arr, start, end - 1);             end++;             start = end;         }           reverse(arr, start, end - 1);           return new String(arr);     }       private void reverse(char[] arr, int start, int end) {         while (start < end) {             char temp = arr[start];             arr[start] = arr[end];             arr[end] = temp;             start++;             end--;         }     } }