input: Write a python function to find pairs of numbers in a list that sum to zero.
  assert algorithm([1, -1, 2, -2, 3, -3]) == [(1, -1), (2, -2), (3, -3)]
  assert algorithm([4, 5, 6, -4, -6]) == [(4, -4), (6, -6)]
  assert algorithm([1, 2, 3, 4, 5]) == []
  assert optimizedAlgorithm([1, -1, 2, -2, 3, -3]) == [(1, -1), (2, -2), (3, -3)]
  assert optimizedAlgorithm([4, 5, 6, -4, -6]) == [(4, -4), (6, -6)]
  assert optimizedAlgorithm([1, 2, 3, 4, 5]) == []
output: def algorithm(lst):
      pairs = []
      for i in range(len(lst)):
          for j in range(i + 1, len(lst)):
              if lst[i] + lst[j] == 0:
                  pairs.append((lst[i], lst[j]))
      return pairs
  
  def optimizedAlgorithm(lst):
      pairs = []
      seen = set()
      for num in lst:
          if -num in seen:
              pairs.append((num, -num) if num > 0 else (-num, num))
          seen.add(num)
      return pairs