[Leet code] Reverse Words in a String III

Leetcode: https://leetcode.com/problems/reverse-words-in-a-string-iii/

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.