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'

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