"""# ### 谜题描述 Kaavi, the mysterious fortune teller, deeply believes that one's fate is inevitable and unavoidable. Of course, she makes her living by predicting others' future. While doing divination, Kaavi believes that magic spells can provide great power for her to see the future. Kaavi has a string T of length m and all the strings with the prefix T are magic spells. Kaavi also has a string S of length n and an empty string A. During the divination, Kaavi needs to perform a sequence of operations. There are two different operations: * Delete the first character of S and add it at the front of A. * Delete the first character of S and add it at the back of A. Kaavi can perform no more than n operations. To finish the divination, she wants to know the number of different operation sequences to make A a magic spell (i.e. with the prefix T). As her assistant, can you help her? The answer might be huge, so Kaavi only needs to know the answer modulo 998 244 353. Two operation sequences are considered different if they are different in length or there exists an i that their i-th operation is different. A substring is a contiguous sequence of characters within a string. A prefix of a string S is a substring of S that occurs at the beginning of S. Input The first line contains a string S of length n (1 ≤ n ≤ 3000). The second line contains a string T of length m (1 ≤ m ≤ n). Both strings contain only lowercase Latin letters. Output The output contains only one integer — the answer modulo 998 244 353. Examples Input abab ba Output 12 Input defineintlonglong signedmain Output 0 Input rotator rotator Output 4 Input cacdcdbbbb bdcaccdbbb Output 24 Note The first test: The red ones are the magic spells. In the first operation, Kaavi can either add the first character \"a\" at the front or the back of A, although the results are the same, they are considered as different operations. So the answer is 6×2=12. Here is a reference code to solve this task. You can use this to help you genereate cases or validate the solution. ```python import sys range = xrange input = raw_input MOD = 998244353 def modder(x): return x if x < MOD else x - MOD S = input() T = input() n = len(S) m = len(T) DP = [[0]*n for _ in range(n + 1)] c = S[0] for i in range(n): DP[1][i] = 2 * (i >= m or c == T[i]) for l in range(1, n): DPl = DP[l] DPlp1 = DP[l + 1] for i in range(n - l + 1): c = S[l] if i and (i - 1 >= m or T[i - 1] == c): DPlp1[i - 1] = modder(DPlp1[i - 1] + DPl[i]) if i + l < n and (i + l >= m or T[i + l] == c): DPlp1[i] += modder(DPlp1[i] + DPl[i]) print sum(DP[j][0] for j in range(m, n + 1)) % MOD ``` 请完成上述谜题的训练场环境类实现,包括所有必要的方法。 """ from bootcamp import Basebootcamp import re import random from bootcamp import Basebootcamp class Ckaaviandmagicspellbootcamp(Basebootcamp): def __init__(self, max_n=3000, min_m=1, default_m=2, default_n=4): self.params = { 'max_n': max_n, 'min_m': min_m, 'default_m': default_m, 'default_n': default_n } def case_generator(self): m = random.randint(self.params['min_m'], self.params['default_m']) n = random.randint(m, self.params['default_n']) # 生成保证至少存在一个解的测试用例 T = ''.join(random.choices('abc', k=m)) # 构造合法S的核心部分(必须与T前缀匹配) op_sequence = [] constructed = list(T) for _ in range(m): op = random.choice(['front', 'back']) op_sequence.append(op) if op == 'front': constructed.pop(0) # 逆向构造 else: constructed.pop() S_core = ''.join(constructed) # 补充随机字符 if n > m: S_core += ''.join(random.choices('abc', k=n - m)) return {"S": S_core, "T": T} @staticmethod def prompt_func(question_case): # 原第44行 S = question_case['S'] T = question_case['T'] prompt = f"""Ckaaviandmagicspell needs to determine the number of valid operation sequences when building string A from "{S}" that results in the prefix "{T}". Each operation chooses to prepend/append the next character from S. The answer must be a single integer within [answer][/answer] tags.""" return prompt @staticmethod def extract_output(output): # 此处修复缩进问题 matches = re.findall(r'\[answer\](.*?)\[/answer\]', output, re.DOTALL) if not matches: return None try: return int(matches[-1].strip()) except ValueError: return None @classmethod def _verify_correction(cls, solution, identity): MOD = 998244353 S = identity['S'] T = identity['T'] n, m = len(S), len(T) # 边界条件处理 if m == 0 or n < m: return solution == 0 # 动态规划验证核心逻辑 dp = [[0]*(n+1) for _ in range(n+1)] dp[0][0] = 1 for step in range(n): for pos in range(n+1): if dp[step][pos] == 0: continue c = S[step] # 前置分支 if pos > 0 and (pos-1 >= m or T[pos-1] == c): dp[step+1][pos-1] = (dp[step+1][pos-1] + dp[step][pos]) % MOD # 后置分支 end_pos = pos + step if end_pos >= m or (end_pos < m and T[end_pos] == c): dp[step+1][pos] = (dp[step+1][pos] + dp[step][pos]) % MOD total = sum(dp[j][0] for j in range(m, n+1)) % MOD return solution == total