Decide Whether a Vehicle Is Ready from Maintenance Open and End Events

A vehicle's maintenance log is a list of events. Each event either opens or ends a maintenance task of one type, such as `oil` or `brake`. The vehicle is ready to go only if every task that was opened has also been ended, and no type ever had two tasks open at the same time. Write a function that decides whether the vehicle is ready to go. ### Function Signature ```python def is_ready_to_go(events: list[list[str]]) -> bool: ``` ### Rules - `events[i] = [action, time, type]`, where `action` is `"open"` or `"end"`, `time` is a non-negative integer written as a decimal string, and `type` names the maintenance task. - The events are not necessarily listed in time order. Process them in increasing order of `time`, comparing times as integers (`"9"` comes before `"10"`). Events with equal times are processed in the order in which they appear in `events`. - Processing `"open"` for a type that already has an open task is a violation: each type can have at most one open task at a time. Different types can be open at the same time. - Processing `"end"` for a type closes that type's open task. If the type has no open task, it is a violation. - Return `True` if no violation occurs and no task is still open after the last event; otherwise return `False`. An empty list returns `True`. - Because of the tie rule, `[["open", "4", "oil"], ["end", "4", "oil"]]` returns `True`, while `[["end", "4", "oil"], ["open", "4", "oil"]]` returns `False`. ### Constraints - `0 <= len(events) <= 10^5` - `action` is exactly `"open"` or `"end"`. - `time` is the decimal form of an integer `0 <= time <= 10^9`, with no leading zeros (`"0"` itself is allowed), so every parsed time fits in a 32-bit signed integer. - `type` has 1 to 20 characters, each a lowercase English letter or an underscore. Types are compared exactly. ### Examples **Example 1** ```text Input: events = [["end", "6", "brake"], ["open", "1", "oil"], ["open", "2", "brake"], ["end", "4", "oil"], ["open", "4", "oil"], ["end", "9", "oil"]] Output: True ``` In time order: `oil` opens at 1, `brake` opens at 2, `oil` ends at 4 and opens again at 4 (the end comes first in the input), `brake` ends at 6, and `oil` ends at 9. No type overlaps itself and nothing is left open. **Example 2** ```text Input: events = [["open", "1", "oil"], ["open", "3", "oil"], ["end", "5", "oil"], ["end", "7", "oil"]] Output: False ``` At time 3 an `oil` task opens while the one opened at time 1 is still open. **Example 3** ```text Input: events = [["open", "2", "tire"], ["end", "8", "tire"], ["open", "5", "brake"]] Output: False ``` The `tire` task is opened and ended, but the `brake` task opened at time 5 is never ended.