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'.*

Source: codewars | Difficulty: EASY

Starter code: def first_dup(s):
	

Solutions:
def first_dup(s):
	for x in s:
		if s.count(x) > 1:
			return x
	return 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('(.).*\\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