input: Write a function to reduce the time complexity of the given Python program that finds the maximum sum of any two distinct elements in an array. The function should take an array as input and return the maximum sum of any two distinct elements in the array.
  assert find_max_sum([1, 2, 3, 4, 5])==9
  assert find_max_sum([10, 20, 30, 40, 50])==90
  assert find_max_sum([5, 2, 1, 4, 3])==8
  assert find_max_sum([7, 7, 7, 7])==0
  assert find_max_sum([])==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 and num != max1:
              max2 = num
      return max1 + max2 if max2 != float('-inf') else 0