Ruby Question
Words in array deleted/popped when sorting through recursion
I am learning Ruby and recursion methods. The problem I am tackling is sorting the words in an array. My recursion methods sort the array correctly, however, every time I run the array through the method, the last word from the initial array ("word") gets deleted:
# Word sorter
def sort(some_array)
recursive_sort(some_array, [])
end
def recursive_sort(unsorted_array, sorted_array)
if unsorted_array.length <= 0
return sorted_array
end
smallest = unsorted_array.pop
unsorted = []
unsorted_array.each do |word|
if word < smallest
unsorted << smallest
smallest = word
else
unsorted << word
end
end
sorted_array << smallest
recursive_sort(unsorted,sorted_array)
end
words = ['hi', 'welcome', 'bye', 'idk', 'where', 'apples', 'bananas']
sort(words)
puts "#{words}"
sort(words)
puts "#{words}"
sort(words)
puts "#{words}"
This is the what happens to the "words" array:
["hi", "welcome", "bye", "idk", "where", "apples"]
["hi", "welcome", "bye", "idk", "where"]
["hi", "welcome", "bye", "idk"]
I've been trying to figure out why this is happening. Any thoughts?
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Answer Source
This is happening because you're passing a reference to an object (your var words) and you're performing a mutation operation on it (pop) which is actually removing the last element of the array each time recursive_sort is called.
To fix this, you'll want to use dup in order to not mutate your original array as such:
def sort(some_array)
given_array = some_array.dup
recursive_sort(given_array, [])
end
More importantly, to print the output of your function you need to include the method call:
words = ['hi', 'welcome', 'bye', 'idk', 'where', 'apples', 'bananas']
puts "#{sort(words)}"
puts "#{sort(words)}"
puts "#{sort(words)}"
puts "#{sort(words)}"
=>
["apples", "bananas", "bye", "hi", "idk", "welcome", "where"]
["apples", "bananas", "bye", "hi", "idk", "welcome", "where"]
["apples", "bananas", "bye", "hi", "idk", "welcome", "where"]
["apples", "bananas", "bye", "hi", "idk", "welcome", "where"]
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