input: Write a function to encode a string into its corresponding ASCII values separated by spaces.
  assert encode_string("hello") == "104 101 108 108 111 "
  assert encode_string("world") == "119 111 114 108 100 "
  assert encode_string("abc") == "97 98 99 "
output: def encode_string(s):
      return ' '.join(str(ord(char)) for char in s) + ' '