Question

I have an exercise in my programming book asking me to sort an array of strings in Ruby without using any of the built in sorting. What I have sorts the top 5 correctly but then just stops and I haven’t been able to figure out why. Here is what I have so far:

numbers = ['one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine', 'ten']

def sortArray myArray
    recursiveSort myArray, []
end

def recursiveSort myArray, sortedArray
    trashArray = myArray
    myArray.each do |num|
        largest = num
        trashArray.each do |comp|
            if comp > largest
                largest = comp
            end
        end
        sortedArray.push(largest)
        trashArray.delete_at(trashArray.index(largest))
    end
    puts sortedArray
end

sortArray numbers

Answer 1

Here’s an example of what’s happening. From my terminal:

$ irb
ruby-1.9.3-p125 :001 > a = [1,2]
 => [1, 2] 
ruby-1.9.3-p125 :002 > b = a
 => [1, 2] 
ruby-1.9.3-p125 :003 > b.delete_at(b.index(1))
 => 1 
ruby-1.9.3-p125 :004 > b
 => [2] 
ruby-1.9.3-p125 :005 > a
 => [2] 

Your variables trashArray and myArray are references to the same object in memory, so you’re removing items from myArray on the line: trashArray.delete_at(trashArray.index(largest)).