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: introductory

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