These are some basic problems working with Ruby's Strings, Arrays and Hashes, from The Odin Project's curriculum
Project 1: Caesar Cipher (cipher.rb)
Implement a caesar cipher that takes in a string and the shift factor and then outputs the modified string
caesar_cipher("What a string!", 5) => "Bmfy f xywnsl!"
Project 2: Stock Picker
Implement a method #stock_picker that takes in an array of stock prices, one for each hypothetical day. It should return a pair of days representing the best day to buy and the best day to sell. Days start at 0.
stock_picker([17,3,6,9,15,8,6,1,10]) => [1,4] # for a profit of $15 - $3 == $12
Project 3: Substrings
Implement a method #substrings that takes a word as the first argument and then an array of valid substrings (your dictionary) as the second argument. It should return a hash listing each substring (case insensitive) that was found in the original string and how many times it was found.
substrings("Howdy partner, sit down! How's it going?", dictionary) => {"down"=>1, "how"=>2, "howdy"=>1,"go"=>1, "going"=>1, "it"=>2, "i"=> 3, "own"=>1,"part"=>1,"partner"=>1,"sit"=>1}