数据结构是以结构化方式组织的数据集合。它分为两种类型，如下所述 -

• 线性数据结构 - 数据以线性方式组织。例如，数组、结构体、堆栈、队列、链表。

• 非线性数据结构 - 数据以分层方式组织。例如，树、图、集合、表。

队列

它是一种线性数据结构，插入在后端完成，删除是在前端完成的。

队列的顺序是 FIFO – 先进先出

操作

• 插入 – 将元素插入队列.
• Delete – 从队列中删除一个元素。

条件

• 队列溢出− 尝试将元素插入满队列。

• 队列处于流状态 − 尝试从空队列中删除元素。

算法

下面给出的是插入 ( ) 的算法 -

• 检查队列溢出。

if (r==n)
printf ("Queue overflow")

• 否则，将一个元素插入到队列中。

q[r] = item
r++

Given below is an algorithm for deletion ( ) −

• Check for queue under flow.

if (f==r)
printf ("Queue under flow")

item = q[f]
f++

下面给出的是display ( )的算法 -

• 检查队列是否为空。

if (f==r)
printf("Queue is empty")

• 否则，打印从‘f’到‘r’的所有元素。

for(i=f; i<r; i++)
printf ("%d", q[i]);

程序

以下是用于在队列中删除元素的C程序 −

#include <stdio.h>
#define MAX 50
void insert();
int array[MAX];
int rear = - 1;
int front = - 1;
main(){
   int add_item;
   int choice;
   while (1){
      printf("1.Insert element to queue 
");
      printf("2.Delete an element from queue
");
      printf("3.Display elements of queue 
");
      printf("4.Quit 
");
      printf("Enter your choice : ");
      scanf("%d", &choice);
      switch (choice){
         case 1:
            insert();
         break;
         case 2:
            delete();
         case 3:
            display();
         break;
         case 4:
            exit(1);
         default:
         printf("Wrong choice 
");
      }
   }
}
void insert(){
   int add_item;
   if (rear == MAX - 1)
      printf("Queue Overflow 
");
   else{
      if (front == - 1)
      /*If queue is initially empty */
      front = 0;
      printf("Inset the element in queue : ");
      scanf("%d", &add_item);
      rear = rear + 1;
      array[rear] = add_item;
   }
}
void display(){
   int i;
   if (front == - 1)
      printf("Queue is empty 
");
   else{
      printf("Queue is : 
");
      for (i = front; i <= rear; i++)
         printf("%d ", array[i]);
         printf("
");
   }
}
void delete(){
   if (front == - 1 || front > rear){
      printf("Queue Underflow 
");
      return ;
   }
   else{
      printf("Element deleted from queue is : %d
",array[front]);
      front = front + 1;
   }
}

输出

当执行上述程序时，会产生以下结果 -

1.Insert element to queue
2.Delete an element from queue
3.Display elements of queue
4.Quit
Enter your choice: 1
Inset the element in queue: 12
1.Insert element to queue
2.Delete an element from queue
3.Display elements of queue
4.Quit
Enter your choice: 1
Inset the element in queue: 23
1.Insert element to queue
2.Delete an element from queue
3.Display elements of queue
4.Quit
Enter your choice: 1
Inset the element in queue: 34
1.Insert element to queue
2.Delete an element from queue
3.Display elements of queue
4.Quit
Enter your choice: 2
Element deleted from queue is: 12
Queue is:
23 34
1.Insert element to queue
2.Delete an element from queue
3.Display elements of queue
4.Quit
Enter your choice: 2
Element deleted from queue is: 23
Queue is:
34
1.Insert element to queue
2.Delete an element from queue
3.Display elements of queue
4.Quit
Enter your choice: 4