Find the first character that repeats in a String and return that character. 

```python
first_dup('tweet') => 't'
first_dup('like') => None
```

*This is not the same as finding the character that repeats first.*
*In that case, an input of 'tweet' would yield 'e'.*

Difficulty: introductory

Starter code:

def first_dup(s):
	

Solutions:
def first_dup(s):
    for x in s:
        if s.count(x) > 1:
            return x
    return None

def first_dup(s):
    return next((x for x in s if s.count(x) > 1),None)

from collections import Counter, OrderedDict

class OC(Counter,OrderedDict): pass

def first_dup(s):
    return next((c for c,n in OC(s).items() if n>1), None)

import re

def first_dup(s):
    return next(iter(re.findall(r'(.).*\1', s)), None)

def first_dup(stg):
    return next((c for c in stg if stg.count(c) > 1), None)

def first_dup(s):
    if s[0] in s[1:]:
        return s[0]
    return len(s)>1 and first_dup(s[1:]) or None

def first_dup(s):
    for i,v in enumerate(s):
        if v in s[i+1:]:
            return v

def first_dup(s):
    for i in [ [s.count(i),i] for i in s  ]:
        if i[0]>1:
            return i[1]


def first_dup(s):
    if not s: return None
    for i in range(len(s)-1):
        if s[i] in s[i+1:]:
            return s[i]
    return None

def first_dup(text):
    for t in text:
        if text.count(t) > 1:
            return t