Write a function that takes a string and returns an array of the repeated characters (letters, numbers, whitespace) in the string.

If a charater is repeated more than once, only show it once in the result array.

Characters should be shown **by the order of their first repetition**. Note that this may be different from the order of first appearance of the character.

Characters are case sensitive.

For F# return a "char list"

## Examples:

```python
remember("apple") => returns ["p"]
remember("apPle") => returns []          # no repeats, "p" != "P"
remember("pippi") => returns ["p","i"]   # show "p" only once
remember('Pippi') => returns ["p","i"]   # "p" is repeated first
```

Difficulty: EASY
Starter code: def remember(str_):
	

Solutions:
def remember(str_):
	seen = set()
	res = []
	for i in str_:
		res.append(i) if i in seen and i not in res else seen.add(i)
	return res


from collections import Counter

def remember(str_):
	(seen, lst) = (Counter(), [])
	for c in str_:
		if seen[c] == 1:
			lst.append(c)
		seen[c] += 1
	return lst


def remember(str_):
	return [c for (i, c) in enumerate(str_) if str_[:i].count(c) == 1]


def remember(stg):
	return [c for (i, c) in enumerate(stg) if stg[:i].count(c) == 1]


def remember(s):
	(li, final) = ([], [])
	for i in s:
		if i not in li:
			li.append(i)
		else:
			final.append(i)
	return sorted(set(final), key=final.index)


def remember(str_):
	d = {}
	seen = set()
	for c in str_:
		if c in seen:
			d[c] = 1
		seen.add(c)
	return list(d)


def remember(str):
	lst = []
	for (i, j) in enumerate(str):
		if j in str[:i] and j not in lst:
			lst.append(j)
	return lst


def remember(str_):
	(first_occured, reported) = ([], [])
	for letter in str_:
		if letter not in first_occured:
			first_occured.append(letter)
		elif letter not in reported:
			reported.append(letter)
	return reported


from enum import Enum
State = Enum('State', 'NONE SEEN APPENDED')

def remember(str_):
	states = {}
	result = []
	for c in str_:
		state = states.get(c, State.NONE)
		if state is State.NONE:
			states[c] = State.SEEN
		elif state is State.SEEN:
			result.append(c)
			states[c] = State.APPENDED
	return result


import re

def remember(str):
	t = []
	for (j, i) in enumerate(str):
		if str[:j + 1].count(i) > 1 and i not in t:
			t.append(i)
	return t