C ++程序使用数组实现队列
队列是包含元素集合的抽象数据结构。队列执行FIFO机制，即，首先插入的元素也将首先删除。换句话说，最近最少添加的元素首先在队列中被删除。
使用数组实现队列的程序如下：
示例
#include <iostream>
using namespace std;
int queue[100], n = 100, front = - 1, rear = - 1;
void Insert() {
int val;
if (rear == n - 1)
cout<<"Queue Overflow"<<endl;
else {
if (front == - 1)
front = 0;
cout<<"Insert the element in queue : "<<endl;
cin>>val;
rear++;
queue[rear] = val;
}
}
void Delete() {
if (front == - 1 || front > rear) {
cout<<"Queue Underflow ";
return ;
} else {
cout<<"Element deleted from queue is : "<< queue[front] <<endl;
front++;;
}
}
void Display() {
if (front == - 1)
cout<<"Queue is empty"<<endl;
else {
cout<<"Queue elements are : ";
for (int i = front; i <= rear; i++)
cout<<queue[i]<<" ";
cout<<endl;
}
}
int main() {
int ch;
cout<<"1) Insert element to queue"<<endl;
cout<<"2) Delete element from queue"<<endl;
cout<<"3) Display all the elements of queue"<<endl;
cout<<"4) Exit"<<endl;
do {
cout<<"Enter your choice : "<<endl;
cin<<ch;
switch (ch) {
case 1: Insert();
break;
case 2: Delete();
break;
case 3: Display();
break;
case 4: cout<<"Exit"<<endl;
break;
default: cout<<"Invalid choice"<<endl;
}
} while(ch!=4);
return 0;
}上面程序的输出如下
1) Insert element to queue 2) Delete element from queue 3) Display all the elements of queue 4) Exit Enter your choice : 1 Insert the element in queue : 4 Enter your choice : 1 Insert the element in queue : 3 Enter your choice : 1 Insert the element in queue : 5 Enter your choice : 2 Element deleted from queue is : 4 Enter your choice : 3 Queue elements are : 3 5 Enter your choice : 7 Invalid choice Enter your choice : 4 Exit
在上面的程序中，该函数Insert()将元素插入队列。如果后方等于n-1，则队列已满，并显示溢出。如果front为-1，则将其递增1。然后，Rear将其递增1，并将元素插入back的索引中。这如下所示-
void Insert() {
int val;
if (rear == n - 1)
cout<<"Queue Overflow"<<endl;
else {
if (front == - 1)
front = 0;
cout<<"Insert the element in queue : "<<endl;
cin>>val;
rear++;
queue[rear] = val;
}
}在函数中Delete()，如果队列中没有元素，则为下溢状态。否则，将显示前面的元素，并且前面的元素将增加一。这如下所示-
void Delete() {
if (front == - 1 || front > rear) {
cout<<"Queue Underflow ";
return ;
}
else {
cout<<"Element deleted from queue is : "<< queue[front] <<endl;
front++;;
}
}在函数中display()，如果front为-1，则队列为空。否则，将使用for循环显示所有队列元素。这如下所示-
void Display() {
if (front == - 1)
cout<<"Queue is empty"<<endl;
else {
cout<<"Queue elements are : ";
for (int i = front; i <= rear; i++)
cout<<queue[i]<<" ";
cout<<endl;
}
}main()如果用户要插入，删除或显示队列，该功能将为用户提供一个选择。根据用户响应，使用开关调用适当的功能。如果用户输入无效的响应，则将其打印出来。下面的代码片段如下-
int main() {
int ch;
cout<<"1) Insert element to queue"<<endl;
cout<<"2) Delete element from queue"<<endl;
cout<<"3) Display all the elements of queue"<<endl;
cout<<"4) Exit"<<endl;
do {
cout<<"Enter your choice : "<<endl;
cin>>ch;
switch (ch) {
case 1: Insert();
break;
case 2: Delete();
break;
case 3: Display();
break;
case 4: cout<<"Exit"<<endl;
break;
default: cout<<"Invalid choice"<<endl;
}
} while(ch!=4);
return 0;
}