Reverse Words in a String
Module 5 · Strings
Problem
Given a string s, return its words in reverse order, joined by
single spaces. s may contain leading, trailing, or repeated spaces; the
output must contain none of those.
Examples
Example 1
Input
"the sky is blue"Output"blue is sky the"Example 2
Input
" hello world "Output"world hello"Example 3
Input
"a good example"Output"example good a"Constraints
1 ≤ n ≤ 10⁴ · letters, digits, spaces · at least one word · follow-up: O(1) auxiliary space if given a mutable char array.
Attempt it first
The pipeline version should take you two minutes with the toolkit lesson. Then think hard about the follow-up — it has a genuinely pretty trick, and you've already met its main ingredient in Rotate Array.