L 379. Design Phone Directory ---------M

Design a Phone Directory which supports the following operations:

 

1. get: Provide a number which is not assigned to anyone.
2. check: Check if a number is available or not.
3. 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]

 

A:

就是用一个 set 来保存所有的数据。

class PhoneDirectory {
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++){
            mySet.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(mySet.empty()){
            return -1;
        }
        int res = *(mySet.begin());
        mySet.erase(res);
        return res;        
    }
    
    /** Check if a number is available or not. */
    bool check(int number) {
        return mySet.find(number) != mySet.end();
    }
    
    /** Recycle or release a number. */
    void release(int number) {
        mySet.insert(number);
    }
private:
    unordered_set<int> mySet;
};

/**
 * 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);
 */