Combine and sort 2 arrays - ruby

Question

This question was asked somewhere else, but I just wanted to check if what I did was applicable given the rspec circumstances:
Write a method that takes two sorted arrays and produces the sorted array that combines both.
Restrictions:
Do not call sort anywhere.
Do not in any way modify the two arrays given to you.
Do not circumvent (2) by cloning or duplicating the two arrays, only to modify the copies.
Hint: you will probably need indices into the two arrays.
combine_arrays([1, 3, 5], [2, 4, 6]) == [1, 2, 3, 4, 5, 6]
Can you just combine the two arrays into a single array and then run a typical bubble sort?
def combine_arrays(arr1,arr2)
final = arr1 + arr2
sorted = true
while sorted do
sorted = false
(0..final.length - 2).each do |x|
if final[x] > final[x+1]
final[x], final[x+1] = final[x+1], final[x]
sorted = true
end
end
end
final
end
p combine_arrays([1,3,5],[2,4,6]) => [1, 2, 3, 4, 5, 6]

Answer 1

Here is a variant which relies solely on Ruby's enumerators. The result is short and sweet.
# merge two sorted arrays into a sorted combined array
def merge(a1, a2)
[].tap do |combined|
e1, e2 = a1.each, a2.each
# The following three loops terminate appropriately because
# StopIteration acts as a break for Kernel#loop.
# First, keep appending smaller element until one of
# the enumerators run out of data
loop { combined << (e1.peek <= e2.peek ? e1 : e2).next }
# At this point, one of these enumerators is "empty" and will
# break immediately. The other appends all remaining data.
loop { combined << e1.next }
loop { combined << e2.next }
end
end
The first loop keeps grabbing the minimum of the two enumerator values until one of the enumerators runs out of values. The second loop then appends all remaining (which may be none) values from the first array's enumerator, the third loop does the same for the second array's enumerator, and tap hands back the resulting array.

Answer 2

Sure, you can do that but you are overlooking a real gimmee - the two arrays you are given will already be sorted.
def combine_arrays(A1, A2)
retVal = Array.CreateInstance(System::Int32, A1.Length + A2.Length - 1)
i = 0
j = 0
while i < A1.Length | j < A2.Length
if i < A1.Length and self.A1(i) < self.A2(j) then
self.retVal(i + j) = self.A1(i)
i += 1
else
self.retVal(i + j) = self.A2(j)
j += 1
end
end
return retVal
end

Answer 3

This is based on the same logic as Dale M's post, but in proper ruby:
def combine_arrays(arr1,arr2)
[].tap do |out|
i1 = i2 = 0
while i1 < arr1.size || i2 < arr2.size
v1 = arr1[i1]
v2 = arr2[i2]
if v1 && (!v2 || v1 < v2)
out << v1
i1 += 1
else
out << v2
i2 += 1
end
end
end
end
combine_arrays([1,3,5], [2,4,6])

Answer 4

Take a look at this one:
def merge(arr1, arr2)
arr2.each { |n| arr1 = insert_into_place(arr1, n) }
arr1.empty? ? arr2 : arr1
end
def insert_into_place(array, number)
return [] if array.empty?
group = array.group_by { |n| n >= number }
bigger = group[true]
smaller = group[false]
if bigger.nil?
number > smaller.last ? smaller << number : smaller.unshift(number)
else
(smaller << number) + bigger
end
end