【Weiss】【第03章】练习3.25：数组模拟队列

【练习3.25】

编写实现队列的例程，使用

a.链表

b.数组

Answer:

在这章一开头就已经写了个链表的队列例程了，所以实际上只要做b小题就可以。

数组模拟队列和链表的两点小不同是：

①、数组空间有限，入队需要检测数组是否已经满

②、数组经过几次操作后，rear可能绕回front前面，所以许多操作都要用模来实现。

测试代码：

#include <iostream>
#include "queue.h"
using namespace std;
using namespace queue;
template class Queue<int>;
int main(void)
{
Simu_Queue<int> test(6);
//测试插入
test.enqueue(2);
test.enqueue(3);
test.enqueue(5);
test.enqueue(7);
test.enqueue(11);
test.enqueue(13);
test.enqueue(17);
test.traverse();
cout << endl;
//测试删除
test.dequeue();
test.dequeue();
test.dequeue();
test.traverse();
cout << endl;
//测试绕数组遍历
test.enqueue(17);
test.enqueue(19);
test.enqueue(23);
test.traverse();
cout << endl;

system("pause");
}

View Code

实现代码：

//练习3.25新增，用数组模拟队列
template <typename T> class Simu_Queue
{
public:
Simu_Queue() :head(nullptr), front(0), rear(0), size(0){}
Simu_Queue(unsigned int _maxsize) :front(0), rear(0), maxsize(_maxsize){ head = new T[maxsize + 1]; }
Simu_Queue(const Simu_Queue& another)
{
front = another.front;
rear = another.rear;
maxsize = another.maxsize;
head = new T[maxsize + 1];
for (unsigned i = 0; i < maxsize + 1; ++i)
head[i] = another.head[i];
}
~Simu_Queue()
{
delete[] head;
front = rear = maxsize = 0;
head = nullptr;
}
Simu_Queue& operator=(const Simu_Queue& another)
{
if (this != &another)
{
delete[] head;
front = another.front;
rear = another.rear;
maxsize = another.maxsize;
head = new T[maxsize + 1];
for (unsigned i = 0; i < maxsize + 1; ++i)
head[i] = another.head[i];
}
}
public:
//返回最大元素量
unsigned int size()const{ return maxsize; }
//返回当前元素量
unsigned int length()const{ return front <= rear ? rear - front : rear + maxsize + 1 - front; }
//判断是否为空
bool empty()const{ return front == rear; }
//入队
bool enqueue(const T &item)
{
if ((rear + 1) % (maxsize + 1) != front)
{
head[rear] = item;
rear = (rear + 1) % (maxsize + 1);
return true;
}
return false;
}
//出队
bool dequeue()
{
if (rear != front)
{
front = (front + 1) % (maxsize + 1);
return true;
}
return false;
}
//输出队列元素
void traverse()const
{
unsigned int temp = front;
while (temp != rear)
{
cout << " " << head[temp] << flush;
temp = (temp + 1) % (maxsize + 1);
}
}
private:
T* head = nullptr;
unsigned int front;
unsigned int rear;
unsigned int maxsize;
};