Given an equation, represented by words on left side and the result on right side.
You need to check if the equation is solvable under the following rules:

Each character is decoded as one digit (0 - 9).
Every pair of different characters they must map to different digits.
Each words[i] and result are decoded as one number without leading zeros.
Sum of numbers on left side (words) will equal to the number on right side (result). 

Return True if the equation is solvable otherwise return False.
 
Example 1:
Input: words = ["SEND","MORE"], result = "MONEY"
Output: true
Explanation: Map 'S'-> 9, 'E'->5, 'N'->6, 'D'->7, 'M'->1, 'O'->0, 'R'->8, 'Y'->'2'
Such that: "SEND" + "MORE" = "MONEY" ,  9567 + 1085 = 10652
Example 2:
Input: words = ["SIX","SEVEN","SEVEN"], result = "TWENTY"
Output: true
Explanation: Map 'S'-> 6, 'I'->5, 'X'->0, 'E'->8, 'V'->7, 'N'->2, 'T'->1, 'W'->'3', 'Y'->4
Such that: "SIX" + "SEVEN" + "SEVEN" = "TWENTY" ,  650 + 68782 + 68782 = 138214
Example 3:
Input: words = ["THIS","IS","TOO"], result = "FUNNY"
Output: true

Example 4:
Input: words = ["LEET","CODE"], result = "POINT"
Output: false

 
Constraints:

2 <= words.length <= 5
1 <= words[i].length, result.length <= 7
words[i], result contains only upper case English letters.
Number of different characters used on the expression is at most 10.

```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 = "class Solution:\n    def isSolvable(self, words: List[str], result: str) -> bool:\n        ## https://leetcode.com/problems/verbal-arithmetic-puzzle/discuss/463921/python-backtracking-with-pruning-tricks\n        ## from low digit position to high digit position, stop searching once (left side sum)%10 did not equal right side at current digit\n        \n        ## mark all initial characters, because not leading zeros are allowed. \n        start = set()\n        for word in words + [result]:\n            if len(word) > 1: ## note: a single 0 is allowed\n                start.add(word[0])\n\n        ## find the maximum length between all words and result\n        n = max(list(map(len, words + [result])))\n        if len(result) < n: ## if the length of result is shorter than other words, it's  not possible\n            return False\n        \n        ## helper function:\n        ## idx: the index currently processing (of words and result)\n        ## i: i-th word in words; when i == len(words) + 1: we have processed all words + result at index \n        ## carry: the carry computed by summing all previous indexes of words\n        def dfs(idx, i, carry, visited, mp):\n            ## base case: when we reach the highest digit (most significant) position\n            ## we should have carry == 0, otherwise the sums are not equal\n            if idx == n: \n                return carry == 0\n            ## when i == len(words) + 1: we have processed all words + result at index\n            ## the specific index of word is word[-idx - 1]\n            ## we check the sum added by carry\n            ## if the sum does not match the digit at result[-idx - 1]\n            ## return False\n            if i == len(words) + 1:\n                sums = sum(mp[word[-idx - 1]] if idx < len(word) else 0 for word in words) + carry\n                if sums % 10 == mp[result[-idx - 1]]:\n                    carry = sums // 10 ## update carry to the next index\n                    ## recursive call to the next index and start from 0-th word\n                    return dfs(idx + 1, 0, carry, visited, mp)\n                return False \n            ## if current word (i-th) has shorter length than index, \n            ## skip it, it will be counted as 0 for this digit\n            if (i < len(words) and idx >= len(words[i])):\n                return dfs(idx, i + 1, carry, visited, mp)\n            \n            \n            tmp = words + [result]\n            ch = tmp[i][-idx-1] ## current character\n            if ch in mp: ## if this character has been assigned a value\n                return dfs(idx, i + 1, carry, visited, mp)\n            \n            ## backtrack: try every possible digit\n            begin = 0\n            if ch in start:\n                begin = 1 ## if it is an initial character of some word\n            for x in range(begin, 10):\n                if x not in visited:\n                    visited.add(x)\n                    mp[ch] = x\n                    if dfs(idx, i + 1, carry, visited, mp.copy()):\n                        return True\n                    visited.remove(x)\n            return False\n        return dfs(0, 0, 0, set(), {})\n            \n        \n"
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'isSolvable'
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: 10788