LeetCode [622] Design Circular Queue

Design your implementation of the circular queue. The circular queue is a linear data structure in which the operations are performed based on FIFO (First In First Out) principle and the last position is connected back to the first position to make a circle. It is also called "Ring Buffer".

One of the benefits of the circular queue is that we can make use of the spaces in front of the queue. In a normal queue, once the queue becomes full, we cannot insert the next element even if there is a space in front of the queue. But using the circular queue, we can use the space to store new values.

Your implementation should support following operations:

• MyCircularQueue(k): Constructor, set the size of the queue to be k.
• Front: Get the front item from the queue. If the queue is empty, return -1.
• Rear: Get the last item from the queue. If the queue is empty, return -1.
• enQueue(value): Insert an element into the circular queue. Return true if the operation is successful.
• deQueue(): Delete an element from the circular queue. Return true if the operation is successful.
• isEmpty(): Checks whether the circular queue is empty or not.
• isFull(): Checks whether the circular queue is full or not.

Example:

MyCircularQueue circularQueue = new MyCircularQueue(3); // set the size to be 3
circularQueue.enQueue(1);  // return true
circularQueue.enQueue(2);  // return true
circularQueue.enQueue(3);  // return true
circularQueue.enQueue(4);  // return false, the queue is full
circularQueue.Rear();  // return 3
circularQueue.isFull();  // return true
circularQueue.deQueue();  // return true
circularQueue.enQueue(4);  // return true
circularQueue.Rear();  // return 4

Note:

• All values will be in the range of [0, 1000].
• The number of operations will be in the range of [1, 1000].
• Please do not use the built-in Queue library.

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class MyCircularQueue { vector<int> vec; int size; int count; int start, end; public: /** Initialize your data structure here. Set the size of the queue to be k. */ MyCircularQueue(int k) { size = k; vec.resize(k); count = 0; start = end = 0; } /** Insert an element into the circular queue. Return true if the operation is successful. */ bool enQueue(int value) { if(count==size) return false; count++; vec[end] = value; if(end==size-1) end = 0; else end++; return true; } /** Delete an element from the circular queue. Return true if the operation is successful. */ bool deQueue() { if(count == 0) return false; count--; if(start==size-1) start = 0; else start++; return true; } /** Get the front item from the queue. */ int Front() { if(count == 0) return -1; return vec[start]; } /** Get the last item from the queue. */ int Rear() { if(count==0) return -1; if(end==0) return vec[size-1]; else return vec[end-1]; } /** Checks whether the circular queue is empty or not. */ bool isEmpty() { return count==0; } /** Checks whether the circular queue is full or not. */ bool isFull() { return count==size; } }; /** * Your MyCircularQueue object will be instantiated and called as such: * MyCircularQueue* obj = new MyCircularQueue(k); * bool param_1 = obj->enQueue(value); * bool param_2 = obj->deQueue(); * int param_3 = obj->Front(); * int param_4 = obj->Rear(); * bool param_5 = obj->isEmpty(); * bool param_6 = obj->isFull(); */