func_code: def intersection(a, b):
      seen = {}
      append = {}
      c = []
      i = 0
      while i < len(a):
          seen[a[i]] = True
      i = i + 1
      i = 0
      while i < len(b):
          if b[i] in seen and b[i] not in append:
              c.append(b[i])
              append[b[i]] = True
          i = i + 1
      return c