队列(循环队列)
声明：图片及内容基于https://www.bilibili.com/video/av94331942ios
原理分析
数据结构
FIFO：先进先出数据结构
front指向头元素的前一个位置ide
rear指向最后一个元素函数
若是用rear=front来判断队列为空仍是满，会出现歧义，其实没法判断spa
此时，若再插入一个元素，则rear=front。code
为了解决这个问题，本问采起留出一个空间不用的策略。及队列容量始终比开辟空间少一。blog
基本数据类型
class CirQueue { private: T* data; int front; int rear; int mSize; public: CirQueue(); CirQueue(int size); ~CirQueue(); bool enQueue(T item); //入队 bool deQueue(T &item); //出队 bool getFront(T& item);//得到队头 bool isEmpty(); bool isFull(); void clearQueue(); void displayQueue(); int queueLength(); //得到队列长度 class Out_of_range{}; //异常类 class Empty{}; //异常类 };
队列初始化
template<class T> CirQueue<T>::CirQueue() { front = rear = 0; mSize = QUEUESIZE; data = new T[mSize]; }
template<class T> CirQueue<T>::CirQueue(int size) { mSize = size; front = rear = 0; data = new T[mSize]; }
析构函数
CirQueue<T>::~CirQueue() { delete[] data; }
入队（尾入）
而使用循环队列能够解决此问题，充分利用空间。队列
bool CirQueue<T>::enQueue(T item) { if (isFull()) throw Out_of_range(); rear = (rear + 1) % mSize; //实现循环队列 data[rear] = item; return true; }
出队（头出）
template<class T> bool CirQueue<T>::deQueue(T& item) { if (isEmpty()) throw Empty(); front = (front + 1) % mSize; item = data[front]; return true; }
获取头元素
template<class T>
bool CirQueue<T>::getFront(T& item) { if (isEmpty()) throw Empty(); int i = (front + 1) % mSize; item = data[i]; return true; }
判断是否为空
rear = front时为空图片
template<class T>
bool CirQueue<T>::isEmpty() { if (rear ==front) return true; return false; }
判断是否为满
template<class T>
bool CirQueue<T>::isFull() { if ((rear + 1) % mSize == front) return true; return false; }
清空队列
void CirQueue<T>::clearQueue() { front = rear = 0; }
打印队列
template<class T>
void CirQueue<T>::displayQueue() { if (isEmpty()) { cout << "队列为空" << endl; return; } int i = (front + 1) % mSize; while (1) { //当front=head时表示下标到达最后一个元素，打印完这个元素之后再退出 cout << data[i] << " "; if (i == rear) break; i = (i + 1) % mSize; } cout << endl; }
获取队列长度
template<class T>
int CirQueue<T>::queueLength() { int length = (rear + mSize - front) % mSize; return length; }
完整代码
#include<iostream>
using namespace std; const int QUEUESIZE = 100; template <class T>
class CirQueue { private: T* data; int front; int rear; int mSize; public: CirQueue(); CirQueue(int size); ~CirQueue(); bool enQueue(T item); bool deQueue(T &item); bool getFront(T& item); bool isEmpty(); bool isFull(); void clearQueue(); void displayQueue(); int queueLength(); class Out_of_range{}; class Empty{}; }; template<class T> CirQueue<T>::CirQueue() { front = rear = 0; mSize = QUEUESIZE; data = new T[mSize]; } template<class T> CirQueue<T>::CirQueue(int size) { mSize = size; front = rear = 0; data = new T[mSize]; } template<class T> CirQueue<T>::~CirQueue() { delete[] data; } template<class T>
bool CirQueue<T>::enQueue(T item) { if (isFull()) throw Out_of_range(); rear = (rear + 1) % mSize; data[rear] = item; return true; } template<class T>
bool CirQueue<T>::deQueue(T& item) { if (isEmpty()) throw Empty(); front = (front + 1) % mSize; item = data[front]; return true; } template<class T>
bool CirQueue<T>::getFront(T& item) { if (isEmpty()) throw Empty(); int i = (front + 1) % mSize; item = data[i]; return true; } template<class T>
bool CirQueue<T>::isEmpty() { if (rear ==front) return true; return false; } template<class T>
bool CirQueue<T>::isFull() { if ((rear + 1) % mSize == front) return true; return false; } template<class T>
void CirQueue<T>::clearQueue() { front = rear = 0; } template<class T>
void CirQueue<T>::displayQueue() { if (isEmpty()) { cout << "队列为空" << endl; return; } int i = (front + 1) % mSize; while (1) { cout << data[i] << " "; if (i == rear) break; i = (i + 1) % mSize; } cout << endl; } template<class T>
int CirQueue<T>::queueLength() { int length = (rear + mSize - front) % mSize; return length; } int main(){ try { CirQueue<int> Queue(3); /*Queue.enQueue(1); Queue.enQueue(2);*/
//int de ; //Queue.deQueue(de); //cout << de << endl; //Queue.displayQueue(); //if (Queue.isFull()) cout << "full"; //cout << Queue.queueLength(); //Queue.clearQueue();
Queue.displayQueue(); } catch (CirQueue<int>::Out_of_range) { cout << "已经满了" << endl; } catch (CirQueue<int>::Empty) { cout << "为空" << endl; } return 0; }