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Sort Squares of an Array

J
J
# Arrays - Sorted Squares

# Algorithm challenge description:
# Given an integer array nums sorted in non-decreasing order
# return an array of the squares of each number sorted in non-decreasing order.
# Input: [4, -1, -9, 2]
# Output: [1, 4, 16, 81]

#
# Approach 1: is using Ruby function (for sure)!
#

def sorted_squares(nums)
  nums.map! { |num| num**2 }.sort
end
print(sorted_squares([4, -1, -9, 2]))

#
# Approach 2: is using bubble sort
#

def bubble_sort(array)
  array_length = array.size
  return array if array_length <= 1

  loop do
    swapped = false
    (array_length - 1).times do |i|
      if array[i] > array[i + 1]
        array[i], array[i + 1] = array[i + 1], array[i]
        swapped = true
      end
    end
    break unless swapped
  end
  array
end

#
# Time complexity: O(n logn), where n is the length of the array.
# Space complexity: O(n) or O(logn)
#

def sorted_squares(nums)
  # This takes O(n)
  nums.map! { |num| num**2 }
  # This can take Ο(n logn)
  bubble_sort(nums)
end
print(sorted_squares([4, -1, -9, 2]))

#
# Approach 3: solving without ruby sort method. Using two-pointers
#
# Time complexity: O(n), where n is the length of the array.
# Space complexity: O(n), if you take output into account and O(1) otherwise.
#
def sorted_squares(nums)
  p1 = 0
  p2 = nums.length - 1
  # since we're returing the result in ascending order,
  # we'll fill in the array from the end
  max_index = p2
  output = []
  while p1 < p2
    nums1_square = nums[p1] * nums[p1]
    nums2_square = nums[p2] * nums[p2]
    if nums1_square < nums2_square
      output[max_index] = nums2_square
      p2 -= 1
    elsif nums1_square > nums2_square
      output[max_index] = nums1_square
      p1 += 1
    else
      output[max_index] = nums1_square
      max_index -= 1
      output[max_index] = nums2_square
      p1 += 1
      p2 -= 1
    end
    max_index -= 1
  end
  # to account for any remaining value left in the input array
  output[max_index] = nums[p1] * nums[p2] if p1 == p2
  output
end

print(sorted_squares([4, -1, -9, 2]))