CircularQueue.cpp

手动封装一个循环顺序队列类：

私有成员属性：存放队列的数组、两个变量分别记录队头和队尾下标
公有成员函数：
- 入队(enqueue)
- 出队(dequeue)
- 展示(show)
- 求队列长度(size())：要求时间复杂度在常量级别
- 判满(bool full())
- 判空(bool empty())

CycleQueue.hCycleQueue.cppmain.cpp

cpp

#ifndef __CYCLE_QUEUE_H__
#define __CYCLE_QUEUE_H__

#define QUEUE_MAXSIZE 20

typedef int datatype;

class CycleQueue {
  int _arr[QUEUE_MAXSIZE];
  int _head_index = 0;
  int _tail_index = 0;

public:
  bool enqueue(datatype data); // 入队
  bool dequeue();              // 出队
  bool is_empty();             // 判断队列是否为空
  bool is_full();              // 判断队列是否为满
  int size();                  // 获取队列中元素个数
  void show();                 // 显示队列中元素
};

#endif

cpp

#include "CycleQueue.h"
#include <iostream>

int CycleQueue::size() {
  return (_tail_index - _head_index + QUEUE_MAXSIZE) % QUEUE_MAXSIZE;
}

bool CycleQueue::is_empty() { return _head_index == _tail_index; }

bool CycleQueue::is_full() {
  return (_tail_index + 1) % QUEUE_MAXSIZE == _head_index;
}

bool CycleQueue::enqueue(datatype data) {
  if (is_full()) {
    std::cout << "Queue is full!" << std::endl;
    return false;
  }

  _arr[_tail_index] = data;
  _tail_index = (_tail_index + 1) % QUEUE_MAXSIZE;
  return true;
}

bool CycleQueue::dequeue() {
  if (is_empty()) {
    std::cout << "Queue is empty!" << std::endl;
    return false;
  }

  _head_index = (_head_index + 1) % QUEUE_MAXSIZE;
  return true;
}

void CycleQueue::show() {
  if (is_empty()) {
    std::cout << "Queue is empty!" << std::endl;
    return;
  }

  int i = _head_index;
  while (i != _tail_index) {
    std::cout << _arr[i] << " ";
    i = (i + 1) % QUEUE_MAXSIZE;
  }
  std::cout << std::endl;
}

cpp

#include "CycleQueue.h"
#include <iostream>

using namespace std;

int main() {
  CycleQueue q;

  cout << "size: " << q.size() << endl;
  cout << "isEmpyt: " << boolalpha << q.is_empty() << endl;

  q.dequeue(); // fail

  q.enqueue(3);
  q.show();
  cout << "size: " << q.size() << endl;
  q.enqueue(5);
  q.show();
  cout << "size: " << q.size() << endl;

  q.dequeue();
  cout << "size: " << q.size() << endl;
  q.show();
  while (!q.is_full()) {
    q.enqueue(8);
  }
  cout << "size: " << q.size() << endl;
  q.show();

  cout << "isFull: " << boolalpha << q.is_full() << endl;
  
  q.dequeue();
  q.enqueue(88);
  q.show();

  q.dequeue();
  q.enqueue(77);
  q.show();

  q.enqueue(66); // fail
  return 0;
}