input: Write a function to improve the time complexity of the given Python program that finds the maximum sum of any two elements in an array. The function should take an array as input and return the maximum sum. If the array is empty, return 0.
  def find_max_sum(arr):
      if not arr:
          return 0
      max_sum = 0
      left = 0
      right = len(arr) - 1
      while left < right:
          max_sum = max(max_sum, arr[left] + arr[right])
          if arr[left] > arr[right]:
              right -= 1
          else:
              left += 1
      return max_sum
  
  assert find_max_sum([3, 4, 5, 1, 2]) == 9
  assert find_max_sum([3, 5, 10, 1, 2]) == 15
  assert find_max_sum([4, 3, 1, 2]) == 6
  assert find_max_sum([3, 5, 4, 1, 2]) == 8
  assert find_max_sum([]) == 0
output: 
  def find_max_sum(arr):
      if not arr:
          return 0
      max1 = max2 = float('-inf')
      for num in arr:
          if num > max1:
              max2 = max1
              max1 = num
          elif num > max2:
              max2 = num
      return max1 + max2
  