A blog about software by Alexander Yaäkov Garber.

String reversal one-liner

ruby

Published on 05 Jul 2020

reverse = ->(str) {Array.new(str.length) {|i| str[(i + 1) * -1]}.join}

reverse["Hello World"]
=> "dlroW olleH"

Steps

Code	Explanation	Return Value
`Array.new`	Create an empty Array	`[]`
`str.length`	The number of characters in a String, including whitespace	`11`
`Array.new(str.length)`	Create an Array with ‘n’ `nil` elements	`[nil, nil, nil... ]`
`str[(i + 1) * -1]`	Replace `nil` with the ‘nth-from-the-end’ character of the String	When `i = 0`, `str[-1]`
`[...].join`	Convert elements to Strings and concatenate them without a delimiter	`[d,l,r,o,W] => 'dlroW'`