Question

link

Problem: Implement a function to find the first character in a string which only appears once.
For example: It returns ‘b’ when the input is “abaccdeff”.

Analysis

Great solution from Ryan:

You can’t know that the character is un-repeated until you’ve processed the whole string, so my suggestion would be…

Keep 2 lists.

One stores chars that appear once, the other list stores repeated chars.

Code is shown below. 

def first_non_repeated_character(string):
  chars = []
  repeated = []
  for character in string:
    if character in chars:
      chars.remove(character)
      repeated.append(character)
    else:
      if not character in repeated:
        chars.append(character)
  if len(chars):
    return chars[0]
  else:
    return False