To-Do List

A to-do app keeps tasks in a typed collection such as List<T>. Each task has a title and a done flag.

Start with an empty list and process the operations, each a command and a title (the title is everything after the first space):

• add <title>: add a pending task at the end, unless a task with that title already exists.
• done <title>: mark that task as done (no effect if it does not exist).
• remove <title>: delete that task (no effect if it does not exist).

Implement todo_list(operations).

Input

operations: The operations. Titles may contain spaces and are compared exactly.

Output

Return the titles of the tasks that are not done, in the order they were added.

Constraints

0 ≤ number of operations ≤ 10,000

Titles have 1 to 50 characters

Examples

Input:
operations = ["add Buy milk", "add Write report", "done Buy milk", "add Call Ada"]

Expected output:
expected = ["Write report", "Call Ada"]

Input:
std::vector<std::string> operations = {"add Buy milk", "add Write report", "done Buy milk", "add Call Ada"};

Expected output:
std::vector<std::string> expected = {"Write report", "Call Ada"};

Input:
string[] operations = new string[] {"add Buy milk", "add Write report", "done Buy milk", "add Call Ada"};

Expected output:
string[] expected = new string[] {"Write report", "Call Ada"};

Input:
operations = ["add Gym", "add Gym", "remove Gym", "done Gym"]

Expected output:
expected = []

Input:
std::vector<std::string> operations = {"add Gym", "add Gym", "remove Gym", "done Gym"};

Expected output:
std::vector<std::string> expected = {};

Input:
string[] operations = new string[] {"add Gym", "add Gym", "remove Gym", "done Gym"};

Expected output:
string[] expected = new string[] {};

References

This challenge is adapted for CodeUtility. Follow the statement and constraints above.

• Microsoft Learn, List<T> class