Backtracking: everyone in the field knows that backtracking engines (PCRE, java, dotnet, javascript, PHP, ruby, python..) are bad because they are the poster child of denial of service attacks. O(2^n) match time complexity is not good. most backtracking implementations are a combination of clever optimizations duct taped to a very slow engine - for simple cases it works well, but using a pattern that is not affected by the optimizations, you get to see what the “real” worst-case behavior looks like.
### from https://tools.ietf.org/html/rfc2246#section-6.2.3.1
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tests: Remove XSTC Python tests。关于这个话题，爱思助手下载最新版本提供了深入分析
At the same time, the company’s weaknesses and growth pain points are equally prominent—and have become the central tests on its path to an IPO. First, control gaps in the franchising model are glaring. With franchised stores accounting for more than 95% of the network, quality control is extremely difficult. In 2024, the “worm incident” at a Beijing franchise store triggered a crisis of trust in the brand; related complaints on the Black Cat platform exceeded 380. Revenue at some outlets plunged by 30%. Meanwhile, in 2025 the ratio of newly opened to closed franchise stores deteriorated from 15:1 to 3:1. Franchisees’ payback periods averaged 13–20 months—and could be longer in top-tier cities due to intense competition. Waning franchisee enthusiasm directly undermines the stability of the company’s core source of revenue.，推荐阅读clash下载获取更多信息