Implement strStr().

Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

Example 1:


Input: haystack = "hello", needle = "ll"
Output: 2


Example 2:


Input: haystack = "aaaaa", needle = "bba"
Output: -1


Clarification:

What should we return when needle is an empty string? This is a great question to ask during an interview.

For the purpose of this problem, we will return 0 when needle is an empty string. This is consistent to C's strstr() and Java's indexOf().

```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     \n     def prefixTable(self, s):\n         t = [0 for _ in s]\n         j = 0\n         i = 1\n         while i < len(s):\n             if j == 0 and s[i] != s[j]:\n                 t[i] = 0\n                 i += 1\n             elif s[i] == s[j]:\n                 t[i] = j + 1\n                 i += 1\n                 j += 1\n             elif j > 0 and s[j] != s[i]:\n                 j = t[j-1]\n         return t\n \n     def find(self, text, pattern):\n         ans = []\n         t = self.prefixTable(pattern)\n         i = j = 0\n         while i < len(text):\n             if text[i] == pattern[j]:\n                 i += 1\n                 j += 1\n \n             if j == len(pattern):\n                 ans.append(i - len(pattern))\n                 j = t[j-1]\n \n             elif i < len(text) and text[i] != pattern[j]:\n                 if j > 0:\n                     j = t[j-1]\n                 else:\n                     i += 1\n         return ans\n     \n     def strStr(self, haystack, needle):\n         """\n         :type haystack: str\n         :type needle: str\n         :rtype: int\n         """\n         if len(needle) == 0:\n             return 0\n         ans = self.find(haystack, needle)\n         return ans[0] if ans else -1\n         # for i in range(len(haystack) - len(needle) + 1):\n         #     if haystack[i: i + len(needle)] == needle:\n         #         return i\n         # return -1\n         \n         \n         # for i in range(len(haystack) - len(needle) + 1):\n         #     if haystack[i : i + len(needle)] == needle:\n         #         return i\n         # return -1\n'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'strStr'
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: 6502