# Process a Mutable Stock-Price Log Build a small stock-price log and process a sequence of queries and updates. ```python def process_stock_log( initial_prices: list[list[str]], operations: list[list[str]], ) -> list[str]: ... ``` Each initial record is `[ticker, date, price]`, where `price` is a positive integer encoded as a string. Initial `(ticker, date)` pairs are unique. Operations have these forms: - `["GET", ticker, date]`: output the price, adding `" (updated)"` if that existing record has ever been changed by `UPDATE`; output `"NONE"` if it is missing. - `["UPDATE", ticker, date, price]`: replace an existing price or create a new record. A newly created record is not marked updated; replacing an existing record marks it updated. - `["CHANGE", ticker, start_date, end_date]`: output the percentage change from the start price to the end price as a sign followed by two decimals and `%`, such as `+25.00%` or `-12.50%`. Output `"NONE"` if either record is missing. - `["COMPARE", ticker1, ticker2, start_date, end_date]`: compute `CHANGE` for both tickers and output the two results joined by `" | "` in ticker order. Dates are opaque strings: equality, not calendar arithmetic, is required. Return outputs from `GET`, `CHANGE`, and `COMPARE` in encounter order. ## Constraints - At most `200_000` initial records and operations in total. - Prices fit in a signed 64-bit integer and are always greater than zero. - Ticker and date strings are non-empty ASCII strings. ## Example ```text Input: initial_prices = [["ACME", "2026-01-01", "100"], ["ACME", "2026-02-01", "125"]] operations = [ ["GET", "ACME", "2026-01-01"], ["CHANGE", "ACME", "2026-01-01", "2026-02-01"], ["UPDATE", "ACME", "2026-01-01", "110"], ["GET", "ACME", "2026-01-01"], ["GET", "OTHER", "2026-01-01"] ] Output: ["100", "+25.00%", "110 (updated)", "NONE"] ```