README_EN.md

379. Design Phone Directory

中文文档

Description

Design a phone directory that initially has maxNumbers empty slots that can store numbers. The directory should store numbers, check if a certain slot is empty or not, and empty a given slot.

Implement the PhoneDirectory class:

• PhoneDirectory(int maxNumbers) Initializes the phone directory with the number of available slots maxNumbers.
• int get() Provides a number that is not assigned to anyone. Returns -1 if no number is available.
• bool check(int number) Returns true if the slot number is available and false otherwise.
• void release(int number) Recycles or releases the slot number.

 

Example 1:

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.

 

Constraints:

• 1 <= maxNumbers <= 104
• 0 <= number < maxNumbers
• At most 2 * 104 calls will be made to get, check, and release.

Solutions

Python3

class PhoneDirectory:
    def __init__(self, maxNumbers: int):
        """
        Initialize your data structure here
        @param maxNumbers - The maximum numbers that can be stored in the phone directory.
        """
        self.provided = [False] * maxNumbers

    def get(self) -> int:
        """
        Provide a number which is not assigned to anyone.
        @return - Return an available number. Return -1 if none is available.
        """
        for i in range(len(self.provided)):
            if not self.provided[i]:
                self.provided[i] = True
                return i
        return -1

    def check(self, number: int) -> bool:
        """
        Check if a number is available or not.
        """
        return not self.provided[number]

    def release(self, number: int) -> None:
        """
        Recycle or release a number.
        """
        self.provided[number] = False


# Your PhoneDirectory object will be instantiated and called as such:
# obj = PhoneDirectory(maxNumbers)
# param_1 = obj.get()
# param_2 = obj.check(number)
# obj.release(number)

Java

class PhoneDirectory {

    private boolean[] provided;

    /**
       Initialize your data structure here
        @param maxNumbers - The maximum numbers that can be stored in the phone directory.
     */
    public PhoneDirectory(int maxNumbers) {
        provided = new boolean[maxNumbers];
    }

    /**
       Provide a number which is not assigned to anyone.
        @return - Return an available number. Return -1 if none is available.
     */
    public int get() {
        for (int i = 0; i < provided.length; ++i) {
            if (!provided[i]) {
                provided[i] = true;
                return i;
            }
        }
        return -1;
    }

    /** Check if a number is available or not. */
    public boolean check(int number) {
        return !provided[number];
    }

    /** Recycle or release a number. */
    public void release(int number) {
        provided[number] = false;
    }
}

/**
 * Your PhoneDirectory object will be instantiated and called as such:
 * PhoneDirectory obj = new PhoneDirectory(maxNumbers);
 * int param_1 = obj.get();
 * boolean param_2 = obj.check(number);
 * obj.release(number);
 */

...