379. Design Phone Directory.cpp

/*
Problem link: https://leetcode.com/problems/design-phone-directory/


Design a Phone Directory which supports the following operations:



get: Provide a number which is not assigned to anyone.
check: Check if a number is available or not.
release: Recycle or release a number.


Example:

// Init a phone directory containing a total of 3 numbers: 0, 1, and 2.
PhoneDirectory directory = new PhoneDirectory(3);

// It can return any available phone number. Here we assume it returns 0.
directory.get();

// Assume it returns 1.
directory.get();

// The number 2 is available, so return true.
directory.check(2);

// It returns 2, the only number that is left.
directory.get();

// The number 2 is no longer available, so return false.
directory.check(2);

// Release number 2 back to the pool.
directory.release(2);

// Number 2 is available again, return true.
directory.check(2);


Constraints:

1 <= maxNumbers <= 10^4
0 <= number < maxNumbers
The total number of call of the methods is between [0 - 20000]
*/


// Solved by Milon

class PhoneDirectory {
public:
    /** Initialize your data structure here
        @param maxNumbers - The maximum numbers that can be stored in the phone directory. */
    PhoneDirectory(int maxNumbers) {
        avail.resize(maxNumbers);
        for(int i = 0; i < maxNumbers; i++) {
            avail[i] = true;
            q.push(i);
        }
    }

    /** Provide a number which is not assigned to anyone.
        @return - Return an available number. Return -1 if none is available. */
    int get() {
        if (q.size() == 0) return -1;
        int num = q.front();
        q.pop();
        avail[num] = false;
        return num;
    }

    /** Check if a number is available or not. */
    bool check(int number) {
        if (avail[number] == true) return true;
        return false;
    }

    /** Recycle or release a number. */
    void release(int number) {
        if (avail[number] == false) {
            avail[number] = true;
            q.push(number);
        }
    }
private:
    vector<bool> avail;
    queue<int> q;
};

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