union_sorted_arrays.rb

# Given two sorted arrays, find their union and intersection.

def union(ar1, ar2)
  i = 0
  j = 0
  l = ar1.length
  m = ar2.length
  common = []
  while i < l && j < m
    if ar1[i] == ar2[j]
      common << ar1[i]
      i += 1
      j += 1

    elsif ar1[i] > ar2[j]
      common << ar2[j]
      j += 1
    else
      common << ar1[i]
      i += 1
    end

  end

  while i < l
    common << ar1[i]
    i += 1
  end

  while j < m
    common << ar2[j]
    j += 1
  end
  common
end

def union_if_duplicates_prsent(ar1, ar2)
  i = 0
  j = 0
  l = ar1.length
  m = ar2.length
  common = []
  while i < l && j < m
    if ar1[i] == ar2[j]
      common << ar1[i]
      i += 1
      j += 1

    elsif ar1[i] > ar2[j]
      common << ar2[j]
      j += 1
    else
      common << ar1[i]
      i += 1
    end

  end

  while i < l
    common << ar1[i]
    i += 1
  end

  while j < m
    common << ar2[j]
    j += 1
  end
  common
end

def intersection(ar1, ar2)
  i = 0
  j = 0
  common = []
  while i < ar1.length
    if ar1[i] == ar2[j]
      common << ar1[i]
      i += 1
      j += 1
    end
    j += 1 while ar1[i] > ar2[j] && j < ar2.length - 1
    i += 1 while ar2[j] > ar1[i] && i < ar1.length - 1

    break if i == ar1.length - 1 || j == ar2.length - 1
  end
  common
end

arr1 = [1, 2, 4, 5, 6]
arr2 = [2, 3, 5, 7]

puts union(arr1, arr2).to_s