*This kata is inspired by [Project Euler Problem #387](https://projecteuler.net/problem=387)*

---

A [Harshad number](https://en.wikipedia.org/wiki/Harshad_number) (or Niven number) is a number that is divisible by the sum of its digits. A *right truncatable Harshad number* is any Harshad number that, when recursively right-truncated, results in a Harshad number at each truncation. By definition, 1-digit numbers are **not** right truncatable Harshad numbers.

For example `201` (which is a Harshad number) yields `20`, then `2` when right-truncated, which are all Harshad numbers. Thus `201` is a *right truncatable Harshad number*.


## Your task

Given a range of numbers (`(a, b)`, both included), return the list of right truncatable Harshad numbers in this range.

```if-not:javascript
Note: there are `500` random tests, with 0 <= `a` <= `b` <= 10^(16)
```
```if:javascript
Note: there are `500` random tests, with `0 <= a <= b <= Number.MAX_SAFE_INTEGER`
```

## Examples

```
0, 20        -->  [10, 12, 18, 20]
30, 100      -->  [30, 36, 40, 42, 45, 48, 50, 54, 60, 63, 70, 72, 80, 81, 84, 90, 100]
90, 200      -->  [90, 100, 102, 108, 120, 126, 180, 200]
200, 210     -->  [200, 201, 204, 207, 209, 210]
1000, 2000   -->  [1000, 1002, 1008, 1020, 1026, 1080, 1088, 1200, 1204, 1206, 1260, 1800, 2000]
2200, 2300   -->  []
9000002182976, 9000195371842  -->  [9000004000000, 9000004000008]
```

---

## My other katas

If you enjoyed this kata then please try [my other katas](https://www.codewars.com/collections/katas-created-by-anter69)! :-)

#### *Translations are welcome!*

```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 functools\nimport itertools\n\n\ndef rthn_between(a, b):\n    k1 = len(str(b))+1\n    k0 = len(str(a))-1\n    harshads = set.union(*map(n_part_harshad, range(k0, k1)))\n    return  sorted( [i for i in harshads if i in range(max(10,a),b+1) ] )\n\n@functools.lru_cache(None)\ndef n_part_harshad(k):\n    vals = set(range(10))\n    if k < 1: return vals - {0}\n    prevs = n_part_harshad(k-1)\n    groups = (10*a+b for a,b in  itertools.product(prevs, vals) )\n    return set(filter(part_harshad, groups))\n\ndef r_harshad(n):\n    k = str(n)\n    vals = (int(k[:i]) for i in range(1,len(k)+1) )\n    return n>9 and  all( map(part_harshad, vals))\n\n@functools.lru_cache(None)\ndef part_harshad(n):\n    return n% dig_sum(n)==0\n    \ndef dig_sum(n):\n    return sum(map(int,str( n)))'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'rthn_between'
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: 32614