力扣622.设计循环队列

力扣622.设计循环队列

• 

  • 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;
      }
  };