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164 lines
3.9 KiB
Python
Executable file
164 lines
3.9 KiB
Python
Executable file
"""#
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### 谜题描述
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The Fair Nut found a string s. The string consists of lowercase Latin letters. The Nut is a curious guy, so he wants to find the number of strictly increasing sequences p_1, p_2, …, p_k, such that:
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1. For each i (1 ≤ i ≤ k), s_{p_i} = 'a'.
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2. For each i (1 ≤ i < k), there is such j that p_i < j < p_{i + 1} and s_j = 'b'.
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The Nut is upset because he doesn't know how to find the number. Help him.
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This number should be calculated modulo 10^9 + 7.
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Input
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The first line contains the string s (1 ≤ |s| ≤ 10^5) consisting of lowercase Latin letters.
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Output
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In a single line print the answer to the problem — the number of such sequences p_1, p_2, …, p_k modulo 10^9 + 7.
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Examples
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Input
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abbaa
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Output
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5
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Input
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baaaa
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Output
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4
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Input
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agaa
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Output
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3
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Note
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In the first example, there are 5 possible sequences. [1], [4], [5], [1, 4], [1, 5].
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In the second example, there are 4 possible sequences. [2], [3], [4], [5].
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In the third example, there are 3 possible sequences. [1], [3], [4].
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Here is a reference code to solve this task. You can use this to help you genereate cases or validate the solution.
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```python
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import math
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import collections
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import bisect
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import heapq
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import time
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import random
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import itertools
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import sys
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mod=1000000007
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s=str(raw_input())
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pos=1
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n=len(s)
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lagataara=1
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p=[]
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for i in xrange(0,n):
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if s[i]=='a':
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lagataara=lagataara+1
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if s[i]=='b':
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pos=(pos*lagataara)%mod
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lagataara=1
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pos=(pos*lagataara+mod)%mod
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print(pos-1)
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```
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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。
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"""
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from bootcamp import Basebootcamp
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import random
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from bootcamp import Basebootcamp
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class Cthefairnutandstringbootcamp(Basebootcamp):
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def __init__(self, max_blocks=5, max_a_per_block=5, max_other_chars=3):
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self.max_blocks = max_blocks
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self.max_a_per_block = max_a_per_block
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self.max_other_chars = max_other_chars
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def case_generator(self):
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k = random.randint(1, self.max_blocks)
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m_list = []
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# 确保至少存在一个块有a（避免全零情况）
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while True:
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m_list = [random.randint(0, self.max_a_per_block) for _ in range(k)]
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if sum(m_list) > 0: # 保证至少有一个a存在
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break
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s_parts = []
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for i in range(k):
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a_part = 'a' * m_list[i]
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other_num = random.randint(0, self.max_other_chars)
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other_chars = ''.join(random.choices(
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[c for c in 'cdefghijklmnopqrstuvwxyz' if c not in {'a', 'b'}],
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k=other_num
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))
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combined = list(a_part + other_chars)
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random.shuffle(combined) # 混合a和其他字符
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s_parts.append(''.join(combined))
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if i < k - 1:
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s_parts.append('b' * random.randint(1, 2)) # 插入1~2个b作为分隔
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s = ''.join(s_parts)
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# 严格按题目规则计算答案
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mod = 10**9 + 7
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product = 1
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for m in m_list:
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product = (product * (m + 1)) % mod
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answer = (product - 1) % mod
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return {
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's': s,
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'correct_answer': answer
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}
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@staticmethod
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def prompt_func(question_case) -> str:
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s = question_case['s']
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return f"""You are given a string composed of lowercase letters. Find the number of strictly increasing index sequences where:
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1. Each index points to an 'a'
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2. Between consecutive indices there's at least one 'b'
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Calculate modulo 1e9+7.
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Input: {s}
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Format your final answer as [answer]number[/answer]. Example: [answer]5[/answer]"""
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@staticmethod
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def extract_output(output):
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import re
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answers = re.findall(r'\[answer\]\s*(\d+)\s*\[/answer\]', output)
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return int(answers[-1]) if answers else None
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@classmethod
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def _verify_correction(cls, solution, identity):
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return solution == identity['correct_answer']
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