Design Phone Directory Python Solution

lcpy gen -n 379   # by problem number
lcpy gen -s design_phone_directory   # by problem name

Input
["PhoneDirectory", "get", "get", "check", "get", "check", "release", "check"]
[[3], [], [], [2], [], [2], [2], [2]]
Output
[null, 0, 1, true, 2, false, null, true]

Explanation
PhoneDirectory phoneDirectory = new PhoneDirectory(3);
phoneDirectory.get();      // It can return any available phone number. Here we assume it returns 0.
phoneDirectory.get();      // Assume it returns 1.
phoneDirectory.check(2);   // The number 2 is available, so return true.
phoneDirectory.get();      // It returns 2, the only number that is left.
phoneDirectory.check(2);   // The number 2 is no longer available, so return false.
phoneDirectory.release(2); // Release number 2 back to the pool.
phoneDirectory.check(2);   // Number 2 is available again, return true.

from collections import deque


class PhoneDirectory:
    # Time: O(1) per operation
    # Space: O(max_numbers)
    def __init__(self, max_numbers: int) -> None:
        self.free = deque(range(max_numbers))
        self.free_set = set(range(max_numbers))

    def get(self) -> int:
        if not self.free:
            return -1
        number = self.free.popleft()
        self.free_set.remove(number)
        return number

    def check(self, number: int) -> bool:
        return number in self.free_set

    def release(self, number: int) -> None:
        if number not in self.free_set:
            self.free_set.add(number)
            self.free.append(number)