Design Phone Directory.cpp

//
//  Design Phone Directory.cpp
//  LeetCode by zhaowei
//
//  Created by Zhao Wei on 9/21/16.
//  Copyright © 2016 Zhao Wei. All rights reserved.
//

///@file    Design Phone Directory
///@author  Wei Zhao
///@date    2016.09.21
///@version 1.0 tle
///@version 1.1 tle
///@version 1.2

/*
 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);
 */

#include <unordered_map>
#include <vector>
#include <set>

using namespace std;

///@note    1. time limit exceeded if use sequence vector to store the numbers.
class PhoneDirectory_tle {
private:
    vector<bool> phone_dict;
public:
    /** Initialize your data structure here
     @param maxNumbers - The maximum numbers that can be stored in the phone directory. */
    PhoneDirectory(int maxNumbers) {
        int i = 0;
        while (i < maxNumbers) {
            phone_dict.push_back(true);
            i++;
        }
    }
    
    /** Provide a number which is not assigned to anyone.
     @return - Return an available number. Return -1 if none is available. */
    int get() {
        for (int i = 0; i < phone_dict.size(); i++) {
            if (phone_dict[i]) {
                phone_dict[i] = false;
                return i;
            }
        }
        return -1;
    }
    
    /** Check if a number is available or not. */
    bool check(int number) {
        if (number >= phone_dict.size()) return false;
        return phone_dict[number];
    }
    
    /** Recycle or release a number. */
    void release(int number) {
        if (number >= phone_dict.size()) return;
        phone_dict[number] = true;
    }
};

///@note    1. try use set(R/B tree) to store phone numbers. Its search, update, insert, delete operation take O(logn) time.
//          2. tle.
class PhoneDirectory_tle2 {
private:
    set<int> ava_phone, unava_phone;
public:
    /** Initialize your data structure here
     @param maxNumbers - The maximum numbers that can be stored in the phone directory. */
    PhoneDirectory(int maxNumbers) {
        for (int i = 0; i < maxNumbers; i++)
            ava_phone.insert(i);
    }
    
    /** Provide a number which is not assigned to anyone.
     @return - Return an available number. Return -1 if none is available. */
    int get() {
        if (!ava_phone.empty()) {
            int new_num = *ava_phone.begin();
            ava_phone.erase(ava_phone.begin());
            unava_phone.insert(new_num);
            return new_num;
        }
        return -1;
    }
    
    /** Check if a number is available or not. */
    bool check(int number) {
        if (find(unava_phone.begin(), unava_phone.end(), number) == unava_phone.end())
            return true;
        else
            return false;
    }
    
    /** Recycle or release a number. */
    void release(int number) {
        if (find(unava_phone.begin(), unava_phone.end(), number) != unava_phone.end()) {
            unava_phone.erase(find(unava_phone.begin(), unava_phone.end(), number));
            ava_phone.insert(number);
        }
        return;
    }
};

///@note    https://discuss.leetcode.com/topic/53136/all-c-solutions-got-lte/2
class PhoneDirectory {
private:
    int* available; //  store the number available
    bool* isAvailable;  //  store the number status
    int n;  //  the available phone numbers' quantity
    
public:
    /** Initialize your data structure here
     @param maxNumbers - The maximum numbers that can be stored in the phone directory. */
    PhoneDirectory(int maxNumbers) {
        n = maxNumbers;
        available = new int[n];
        isAvailable = new bool[n];
        for (int i = 0; i < n; i++) {
            available[i] = i;
            isAvailable[i] = true;
        }
    }
    
    ~PhoneDirectory() {
        delete []available;
        delete []isAvailable;
    }
    
    /** Provide a number which is not assigned to anyone.
     @return - Return an available number. Return -1 if none is available. */
    int get() {
        if (!n) {
            return -1;
        }
        int number = available[--n];
        isAvailable[number] = false;
        return number;
    }
    
    /** Check if a number is available or not. */
    bool check(int number) {
        return isAvailable[number];
    }
    
    /** Recycle or release a number. */
    void release(int number) {
        if (!isAvailable[number]) {
            isAvailable[number] = true;
            available[n++] = number;
        }
    }
};

/**
 * 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);
 */