input: Write a function to improve the provided Python program to reduce its time complexity. The function should find the maximum sum of any two distinct elements in a given array. If the array is empty or contains only one element, the function should return 0.
  assert find_max_sum([1, 2, 3, 4, 5])==9
  assert find_max_sum([10, 2, 9, 1, 5])==19
  assert find_max_sum([-1, -2, -3, -4, -5])==-3
  assert find_max_sum([])==0
  assert find_max_sum([7])==0
output: def find_max_sum(arr):
      if len(arr) < 2:
          return 0
      max1, max2 = float('-inf'), float('-inf')
      for num in arr:
          if num > max1:
              max2 = max1
              max1 = num
          elif num > max2:
              max2 = num
      return max1 + max2