Email (Multi-part)

Email (Multi-part) Implement a set of email-related functions/logic (3 parts). Part 1: Parse & validate Given a string s, determine whether it is a valid email. Minimum rules: Contains exactly one @ Non-empty local-part and domain Domain contains at least one ., and . is not the first or last character Output true/false. Part 2: Canonicalization Given an email string s, output its canonical form: Case-insensitive (convert to lowercase) Remove +tag from the local-part (delete + and everything after it) Remove all . characters from the local-part Example: "John.Smith+promo@Gmail.com" -> "johnsmith@gmail.com" Part 3: Unique count Given N emails, filter out invalid ones, canonicalize valid ones (Part 2), and output the number of distinct canonical emails. Input From stdin: Line 1: integer N Next N lines: one email string per line Output An integer: number of distinct canonical emails. Constraints 1 <= N <= 2e5 Each string length <= 200 Aim for O(total_length) or near-linear time. Example Input 6 John.Smith+promo@Gmail.com johnsmith@gmail.com alice@leetcode.com alice+spam@leetcode.com bad-email x@a Output 2 Example Input 6 John.Smith+promo@Gmail.com johnsmith@gmail.com alice@leetcode.com alice+spam@leetcode.com bad-email x@a Output 2