极客笔记C++程序用数组实现队列
一个 队列 是一个包含一组元素的抽象数据结构。队列实现了FIFO机制，即先插入的元素也会先被删除。换句话说，在队列中最近添加的元素会首先被移除。
以下是一个用数组实现队列的程序示例−
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;
}
以上程序的输出结果如下：
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
在上述程序中，函数 Insert() 将一个元素插入队列中。如果队尾等于n-1，则队列已满，显示溢出。如果队首是-1，则将其增加1。然后队尾增加1，并在队尾的索引处插入元素。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Delete()中，如果队列中没有元素，则为下溢条件。否则，将显示队列前面的元素，并将前面的指针增加一。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Display()中，如果front是-1，则队列为空。否则，使用for循环显示所有队列元素。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;
}
}
函数main()提供给用户选择是否要插入、删除或显示队列。根据用户的响应，使用switch调用相应的函数。如果用户输入无效的响应，则打印该信息。以下是此代码片段的代码片段。
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;
}