力扣622.设计循环队列

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  • 通过数组索引构建一个虚拟的首尾相连的环
  • 当front = rear时 队列为空
  • 当front = rear + 1时 队列为满 (最后一位不存)

•   class MyCircularQueue {int front;int rear;int capacity;vector<int> elements;public:MyCircularQueue(int k) {//最后一位不存元素 多开一个capacity = k+1;elements = vector<int>(capacity);rear = front = 0;}bool enQueue(int value) {if(isFull())return false;elements[rear] = value;rear = (rear + 1) % capacity;return true;}bool deQueue() {if(isEmpty())return false;front = (front + 1) % capacity;return true;}int Front() {if(isEmpty())return -1;return elements[front];}int Rear() {if(isEmpty())return -1;return elements[(rear - 1 + capacity) % capacity];}bool isEmpty() {return rear == front;}bool isFull() {return ((rear + 1) % capacity) == front;}};