## Task

Complete the function that receives an array of strings (`arr`) as an argument and returns all the valid Roman numerals.

Basic Roman numerals are denoted as:

```
I: 1, V: 5, X: 10, L: 50, C: 100, D: 500, M: 1000
```

For the purposes of this kata we will consider valid only the numbers in range 0 - 5000 (both exclusive) since numbers >= 5000 were written in a different way (you had to place a heavy bar over the numeral that meant it was multiplied with 1000).

There are other ways of tackling this problem but the easiest is probably writing a Regular Expression.

### Let's break the problem down:

To match a set of characters `/[1-9]/`(single digits) you should take into consideration the Roman numbers `I, II, III, IV, V, VI, VII, VIII, IX`. This could be done by testing with `/IX|IV|V?I{0,3}/`. This part `/I{0,3}/` matches `I, II or III` but we have a `V` appearing 0 or 1 times because of the `?` so `/V?I{0,3}/` would match `I,II,III,V,VI,VII or VIII`. However there is one flaw with this. Do you see it? It is the fact that it would also match an empty string `""` because of the {0,3}. In order to pass the tests you will have to **filter out the empty strings** as well. So the entire part matches `I to IX`(inclusive) but what about larger digits?

Use the same logic for the digit in the tens place and the hundreds place. Be sure to wrap each part (units, tens, hundreds, thousands) in a pair of braces `(IX|IV|V?I{0,3})` and for the digit in the thousands place the logic is pretty straight forward, you just have to match `M` 0 to 4 times (since 5000 is not included). Wrap everything up with `^` and `$` to make sure you match the entire string (^ matches from the beginning of the string, while $ denotes the end, meaning there is nothing after that sign.

## Examples

```
["I", "IIV", "IVI", "IX", "XII", "MCD"] ==> ["I", "IX", "XII", "MCD"]

["MMMMCMXCIX", "MMDCXLIV", "MMCIX", "CLD", "LCD"]) ==> ["MMMMCMXCIX", "MMDCXLIV", "MMCIX"]
```

Good luck!

```python

USER_FILENAME = "<user_code>"
import sys, json, builtins
import math, heapq, bisect, itertools, functools, collections, statistics, fractions, decimal, operator, array, random, re, string, os, pathlib
try:
    import resource as _res
except Exception:
    _res = None
from collections import Counter, defaultdict, deque, OrderedDict
from functools import lru_cache, reduce
from itertools import accumulate, permutations, combinations, product
from math import gcd, ceil, floor, sqrt
from decimal import Decimal
try:
    from typing import *
except Exception:
    pass
try:
    sys.setrecursionlimit(1_000_000)
except Exception:
    pass
try:
    import site as _site
    try:
        _sys_sites = _site.getsitepackages() if hasattr(_site, "getsitepackages") else []
        for _p in _sys_sites:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
    try:
        _usp = _site.getusersitepackages()
        if isinstance(_usp, str):
            _usp = [_usp]
        for _p in _usp:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
except Exception:
    pass

def _disabled_input(*args, **kwargs):
    raise RuntimeError("input() is disabled in callable mode")
builtins.input = _disabled_input

ns = {"__name__": "__judge__"}  # prevent if __name__ == "__main__" blocks
for _k, _v in list(globals().items()):
    if not _k.startswith("_"):
        ns[_k] = _v
_CODE = 'import re\n\nPATTERN = re.compile("^"\n    "M{0,4}"             # thousands\n    "(CM|CD|D?C{,3})"    # hundreds\n    "(XC|XL|L?X{,3})"    # tens\n    "(IX|IV|V?I{,3})"    # units\n    "$")\n\ndef valid_romans(arr):\n    return [e for e in arr if e and PATTERN.match(e)]'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'valid_romans'
if _fn_name:
    if "Solution" in ns:
        try:
            _obj = ns["Solution"]()
            if hasattr(_obj, _fn_name):
                _target = getattr(_obj, _fn_name)
        except Exception:
            _target = None
    if _target is None and _fn_name in ns and callable(ns[_fn_name]):
        _target = ns[_fn_name]
# Fallback: if there's exactly one user-defined function, use it
if _target is None:
    _cands = [v for k, v in ns.items() if callable(v) and getattr(v, "__module__", "") in ("__judge__", "__main__")]
    _user_funcs = [c for c in _cands if getattr(c, "__name__", "").startswith("_") is False]
    if len(_user_funcs) == 1:
        _target = _user_funcs[0]
if _target is None:
    raise RuntimeError(f"Could not resolve callable '{_fn_name}'")

_raw = sys.stdin.read().strip()
if _raw:
    _parsed = json.loads(_raw)
    if isinstance(_parsed, dict):
        _kwargs = _parsed.get("kwargs", {})
        _args = _parsed.get("args", [])
    else:
        _args, _kwargs = _parsed, {}
else:
    _args, _kwargs = [], {}
if not isinstance(_args, (list, tuple)):
    _args = [_args]
_res = _target(*_args, **_kwargs)
try:
    sys.stdout.write(repr(_res) + "\n")
except Exception:
    pass

```

Measured memory_bytes: 6558