Queue implementation in C
Queue is another linear data structures. Have you stand in a queue. People who stands in the front will go first. Same principle is applicable here. This principle is called FIFO(First In First Out).
Functions and variables in queue:
- First
element denotes front.
- Last
element represents rear.
- To
insert an element in rear end use enqueue ().
- To delete
an element, consider dequeue() function.
- ‘peek()’
is a function which makes the user to view the front element. It doesn’t
delete the element.
Let us create a queue using arrays in C.
Program:
#include <stdio.h>
#include <stdlib.h>
#define MAX 9 // Let
us declare the maximum size of queue
int queue[MAX];
int front = -1, rear = -1;
// queue is full or not
int isFull() {
return (rear ==
MAX - 1);
}
// Queue empty checking
int isEmpty() {
return (front ==
-1 || front > rear);
}
// Add the elements to the queue
void enqueue(int data) {
if (isFull()) {
printf("Queue is full!\n");
return;
}
if (front == -1)
front = 0;
queue[++rear] =
data;
printf("%d
inserted into queue.\n", data);
}
// Delete an element from queue
void dequeue() {
if (isEmpty()) {
printf("Queue is empty!\n");
return;
}
printf("%d
removed from queue.\n", queue[front++]);
}
// To view the front element
void peek() {
if (isEmpty()) {
printf("Queue is empty!\n");
return;
}
printf("Front
element is: %d\n", queue[front]);
}
// Print the queue elements
void display() {
if (isEmpty()) {
printf("Queue is empty!\n");
return;
}
printf("Queue
elements: ");
for (int i =
front; i <= rear; i++) {
printf("%d ", queue[i]);
}
printf("\n");
}
int main() {
enqueue(100);
enqueue(24);
enqueue(36);
enqueue(120);
enqueue(67);
display();
dequeue();
peek();
dequeue();
peek();
display();
return 0;
}
Output:
100 inserted into queue.
24 inserted into queue.
36 inserted into queue.
120 inserted into queue.
67 inserted into queue.
Queue elements: 100 24 36 120 67
100 removed from queue.
Front element is: 24
24 removed from queue.
Front element is: 36
Queue elements: 36 120 67
Yes. The queue implementation in C is successful. You can
easily understand this concept. Keep Coding!!!
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