comparison of Fixnum with nil failed (ArgumentError) - ruby

Question

i'm starting in ruby and i don't know why this is happening.
this is my code.
def buble_sort(a)
i = 0
print a.size()
while i < a.size() do
if a[i] > a[i+1] then
temp = a[i]
a[i] = temp
a[i+1] = a[i]
end
i = i + 1
end
return a
end
puts "Amount of elements in your array"
n = gets.chomp.to_i
a = []
n.times do |num|
puts "input your element #{num}"
a <<gets.chomp.to_i
end
puts a
a = buble_sort(a)
puts "Array sorted #{a}"
And the output give me this error:
4burbuja.rb:6:in >': comparison of Fixnum with nil failed (ArgumentError)
from burbuja.rb:6:inbuble_sort'
from burbuja.rb:24:in `'

Answer 1

I understand that you are learning ruby and want to implement your own bubble sort. a.sort is easy but doesn't teach you anything. I'm glad you are learning by doing! There is a flaw in your bubble sort method. You are incrementing i and using it as an index for your array on each iteration. It could take many iterations to complete, in the worst case it will take n**2 (n squared) iterations which will clearly be more than the elements in your array. However if your code worked as I expect you expected it to run it would only make one pass on the array.
This is a classic ruby bubble sort. (with your having the user fill the array from console)
Notice that we continue to process the ENTIRE array multiple times until we no longer need to swap any values.
def bubble_sort(array)
n = array.length
puts "Sorting your array of #{n} items"
loop do #will loop forever till we break
#When we go through the entire array
#and don't have to swap then the array
#is sorted
swapped = false
(n-1).times do |i|
print "*" #just to illustrate how many iterations occur
if array[i] > array[i+1]
array[i], array[i+1] = array[i+1], array[i] #swap these values, no pesky temp variable
swapped = true
end
end
break if not swapped #we are done exit the loop
end
array #return the sorted array
end
puts "Amount of elements in your array"
n = gets.chomp.to_i
a = []
n.times do |num|
puts "input your element #{num}"
a <<gets.chomp.to_i
end
puts a
a = bubble_sort(a)
puts "Array sorted #{a}"
Here is an example of it being run via console
Cyclops% ruby sort_test.rb
Amount of elements in your array
6
input your element 0
5465463
input your element 1
3421
input your element 2
432143
input your element 3
234123
input your element 4
645
input your element 5
1
5465463
3421
432143
234123
645
1
Sorting your array of 6 items
******************************
Array sorted [1, 645, 3421, 234123, 432143, 5465463]
Cyclops%