Count substrings and generate TOC

Solve the following two coding problems. 1. **Count valid binary substrings** Given a string `s` consisting only of `'0'` and `'1'`, count how many substrings satisfy both conditions: - The substring contains the same number of `0`s and `1`s. - All `0`s in the substring are contiguous, and all `1`s in the substring are contiguous. In other words, a valid substring must consist of exactly two consecutive groups, such as `"0011"`, `"1100"`, `"01"`, or `"10"`. Return the total number of valid substrings. 2. **Generate a table of contents** You are given an array of strings `lines`, where each element represents one line in a document. Build a table of contents using the following rules: - A line starting with `"##"` is a **section** and belongs to the most recent chapter. - Otherwise, a line starting with `"#"` is a **chapter**. - All other lines should be ignored. Number chapters and sections in the order they appear: - A chapter should be output as `"<chapter_number>. <title>"` - A section should be output as `"<chapter_number>.<section_number>. <title>"` When a new chapter appears, its section numbering starts again from 1. Return the generated table of contents as an array of strings.