# Sort the arr from lowest to highest
def mergesort(arr)
  return arr if arr.size <= 1
  middle   = arr.size / 2
  left  = arr[0, middle]
  right = arr[middle, arr.size]
  merge(mergesort(left), mergesort(right))
end

def merge(left, right)
  sorted = []
  until left.empty? || right.empty?
    if left.first <= right.first
      sorted << left.shift
    else
      sorted << right.shift
    end
  end
  sorted + left + right
end

# Find the maximum
def maximum(arr)
  mergesort(arr).last
end

def minimum(arr)
  mergesort(arr).first
end

# expect it to return 42 below

result = maximum([2, 42, 22, 02])
puts "max of 2, 42, 22, 02 is: #{result}"

# expect it to return 2 below
result = minimum([2, 42, 22, 02])
puts "min of 2, 42, 22, 02 is: #{result}"

# expect it to return nil when empty arr is passed in
result = maximum([])
puts "max on empty set is: #{result.inspect}"

result = minimum([])
puts "min on empty set is: #{result.inspect}"

result = maximum([-23, 0, -3])
puts "max of -23, 0, -3 is: #{result}"

result = maximum([6])
puts "max of just 6 is: #{result}"