FIFO队列

循环队列是一种线性数据结构，其操作表现基于 FIFO（先进先出）原则并且队尾被连接在队首之后以形成一个循环。它也被称为“环形缓冲器”。

题目：设计循环队列

  1. class MyCircularQueue {
  2. private:
  3.     vector<int> data;
  4.     int head;
  5.     int tail;
  6.     int size;
  7. public:
  8.     /** Initialize your data structure here. Set the size of the queue to be k. */
  9.     MyCircularQueue(int k) {
  10.         data.resize(k);
  11.         head = -1;
  12.         tail = -1;
  13.         size = k;
  14.     }
  16.     /** Insert an element into the circular queue. Return true if the operation is successful. */
  17.     bool enQueue(int value) {
  18.         if (isFull()) {
  19.             return false;
  20.         }
  21.         if (isEmpty()) {
  22.             head = 0;
  23.         }
  24.         tail = (tail + 1) % size;
  25.         data[tail] = value;
  26.         return true;
  27.     }
  29.     /** Delete an element from the circular queue. Return true if the operation is successful. */
  30.     bool deQueue() {
  31.         if (isEmpty()) {
  32.             return false;
  33.         }
  34.         if (head == tail) {
  35.             head = -1;
  36.             tail = -1;
  37.             return true;
  38.         }
  39.         head = (head + 1) % size;
  40.         return true;
  41.     }
  43.     /** Get the front item from the queue. */
  44.     int Front() {
  45.         if (isEmpty()) {
  46.             return -1;
  47.         }
  48.         return data[head];
  49.     }
  51.     /** Get the last item from the queue. */
  52.     int Rear() {
  53.         if (isEmpty()) {
  54.             return -1;
  55.         }
  56.         return data[tail];
  57.     }
  59.     /** Checks whether the circular queue is empty or not. */
  60.     bool isEmpty() {
  61.         return head == -1;
  62.     }
  64.     /** Checks whether the circular queue is full or not. */
  65.     bool isFull() {
  66.         return ((tail + 1) % size) == head;
  67.     }
  68. };
  70. /**
  71.  * Your MyCircularQueue object will be instantiated and called as such:
  72.  * MyCircularQueue obj = new MyCircularQueue(k);
  73.  * bool param_1 = obj.enQueue(value);
  74.  * bool param_2 = obj.deQueue();
  75.  * int param_3 = obj.Front();
  76.  * int param_4 = obj.Rear();
  77.  * bool param_5 = obj.isEmpty();
  78.  * bool param_6 = obj.isFull();
  79.  */