Given two strings text1 and text2, return the length of their longest common subsequence.
A subsequence of a string is a new string generated from the original string with some characters(can be none) deleted without changing the relative order of the remaining characters. (eg, "ace" is a subsequence of "abcde" while "aec" is not). A common subsequence of two strings is a subsequence that is common to both strings.
 
If there is no common subsequence, return 0.
 
Example 1:
Input: text1 = "abcde", text2 = "ace" 
Output: 3  
Explanation: The longest common subsequence is "ace" and its length is 3.

Example 2:
Input: text1 = "abc", text2 = "abc"
Output: 3
Explanation: The longest common subsequence is "abc" and its length is 3.

Example 3:
Input: text1 = "abc", text2 = "def"
Output: 0
Explanation: There is no such common subsequence, so the result is 0.

 
Constraints:

1 <= text1.length <= 1000
1 <= text2.length <= 1000
The input strings consist of lowercase English characters only.

```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    # approach 3\n    def longestCommonSubsequence(self, s1: str, s2: str) -> int:\n        def print_grid(grid):\n            for row in grid:\n                print(row)\n        \n        dp_row = [0] * (len(s2) + 1)\n        dp_row_pre = [0] * (len(s2) + 1)\n        N, M = len(s1), len(s2)\n        for i in range(N - 1, -1, -1):\n            for j in range(M - 1, -1, -1):\n                if s1[i] == s2[j]:\n                    dp_row[j] = dp_row_pre[j + 1] + 1\n                else:\n                    dp_row[j] = max(dp_row_pre[j], dp_row[j + 1])\n            dp_row_pre, dp_row = dp_row, dp_row_pre\n                # print(\\"update row=\\", i, \\", col=\\", j)\n                # print_grid(dp_grid)\n        return dp_row_pre[0]\n        \n    # approach 1: recursive memorization\n#     def longestCommonSubsequence(self, text1: str, text2: str) -> int:\n        \n#         @lru_cache(maxsize=None)\n#         def memo_solve(p1, p2):\n#             if p1 == len(text1) or p2 == len(text2):\n#                 return 0\n            \n#             # option 1: we don\'t include text1[p1] in the solution\n#             option_1 = memo_solve(p1 + 1, p2)\n            \n#             # option 2: we include p1 in the solution, as long as there is a match in p2\n#             first_occurrence = text2.find(text1[p1], p2)\n#             option_2 = 0\n#             if first_occurrence != -1:\n#                 option_2 = 1 + memo_solve(p1 + 1, first_occurrence + 1)\n            \n#             return max(option_1, option_2)\n        \n#         return memo_solve(0, 0)\n    \n      # approach 2\n#     def longestCommonSubsequence(self, s1: str, s2: str) -> int:\n        \n#         @lru_cache(maxsize=None)\n#         def mem_solve(p1: int, p2: int) -> int:\n#             # base case \n#             if p1 == len(s1) or p2 == len(s2):\n#                 return 0\n            \n#             # option 1 match the first letter\n#             if s1[p1] == s2[p2]:\n#                 return 1 + mem_solve(p1 + 1, p2 + 1)\n            \n#             # option 2\n#             return max(mem_solve(p1, p2 + 1), mem_solve(p1 + 1, p2))\n        \n#         return mem_solve(0, 0)\n        \n'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'longestCommonSubsequence'
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: 5840