Reverse Words in a String

Problem Statement
Given an array of characters representing words separated by single spaces, reverse the order of words in-place (modify the input array directly without extra space). Do not allocate additional arrays or strings. Each word consists of lowercase English letters and is separated by exactly one space.[1][4]

Approach Overview
Use two pointers with a two-step process: first reverse characters within each individual word, then reverse the entire array. This achieves word order reversal while restoring correct character order in each word.[1]

Input/Output Examples

| Input Array | Output Array | |-------------|--------------| | ['t','h','e',' ','s','k','y',' ','i','s',' ','b','l','u','e'] | ['b','l','u','e',' ','i','s',' ','s','k','y',' ','t','h','e'] | | ['c','a','t',' ','i','s'] | ['i','s',' ','c','a','t'] |
[1]

Constraints

• 1 <= s.length <= 5 * 10^4
• s[i] is either ' ' (space) or a lowercase English letter
• Words are separated by exactly one space
• Leading/trailing spaces are absent
• Must operate in-place with O(1) extra space[1]