#include <stdio.h>
#include <stdlib.h>

#define MAX_SIZE 100

// Define the structure for the queue
struct Queue {
    int arr[MAX_SIZE];
    int front, rear;
};

// Function to initialize a queue
void initialize(struct Queue *queue) {
    queue->front = -1;
    queue->rear = -1;
}

// Function to check if the queue is empty
int isEmpty(struct Queue *queue) {
    return queue->front == -1;
}

// Function to check if the queue is full
int isFull(struct Queue *queue) {
    return (queue->rear + 1) % MAX_SIZE == queue->front;
}

// Function to enqueue an element into the queue
void enqueue(struct Queue *queue, int value) {
    if (isFull(queue)) {
        printf("Queue overflow: Cannot enqueue element %d\n", value);
        return;
    }
    
    if (isEmpty(queue)) {
        queue->front = 0;
    }
    
    queue->rear = (queue->rear + 1) % MAX_SIZE;
    queue->arr[queue->rear] = value;
}

// Function to dequeue an element from the queue
int dequeue(struct Queue *queue) {
    if (isEmpty(queue)) {
        printf("Queue underflow: Cannot dequeue element\n");
        return -1;
    }
    
    int value = queue->arr[queue->front];
    
    if (queue->front == queue->rear) {
        queue->front = -1;
        queue->rear = -1;
    } else {
        queue->front = (queue->front + 1) % MAX_SIZE;
    }
    
    return value;
}

// Function to display the elements in the queue
void display(struct Queue *queue) {
    if (isEmpty(queue)) {
        printf("Queue is empty\n");
        return;
    }
    
    int current = queue->front;
    printf("Queue elements: ");
    
    while (current != queue->rear) {
        printf("%d ", queue->arr[current]);
        current = (current + 1) % MAX_SIZE;
    }
    printf("%d\n", queue->arr[current]);
}

int main() {
    struct Queue queue;
    initialize(&queue);
    
    // Enqueue elements
    enqueue(&queue, 10);
    enqueue(&queue, 20);
    enqueue(&queue, 30);
    
    // Display queue
    display(&queue);
    
    // Dequeue elements
    printf("Dequeued element: %d\n", dequeue(&queue));
    printf("Dequeued element: %d\n", dequeue(&queue));
    
    // Display queue after dequeue
    display(&queue);
    
    return 0;
}

C Language online compiler

Write, Run & Share C Language code online using OneCompiler's C online compiler for free. It's one of the robust, feature-rich online compilers for C language, running the latest C version which is C18. Getting started with the OneCompiler's C editor is really simple and pretty fast. The editor shows sample boilerplate code when you choose language as 'C' and start coding!

Read inputs from stdin

OneCompiler's C online editor supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample C program which takes name as input and print your name with hello.

#include <stdio.h>
int main()
{
    char name[50];
    printf("Enter name:");
    scanf("%s", name);
    printf("Hello %s \n" , name );
    return 0;
    
}

About C

C language is one of the most popular general-purpose programming language developed by Dennis Ritchie at Bell laboratories for UNIX operating system. The initial release of C Language was in the year 1972. Most of the desktop operating systems are written in C Language.

Key features:

  • Structured Programming
  • Popular system programming language
  • UNIX, MySQL and Oracle are completely written in C.
  • Supports variety of platforms
  • Efficient and also handle low-level activities.
  • As fast as assembly language and hence used as system development language.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition if-else is used.

if(conditional-expression) {
   // code
} else {
   // code
}

You can also use if-else for nested Ifs and if-else-if ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to if-else-if ladder.

switch(conditional-expression) {    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
...    
    
default:     
 // code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  // code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while(condition) {  
 // code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {
  // code 
} while (condition);

Arrays

Array is a collection of similar data which is stored in continuous memory addresses. Array values can be fetched using index. Index starts from 0 to size-1.

Syntax

One dimentional Array:

data-type array-name[size];

Two dimensional array:

data-type array-name[size][size];

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity.

Two types of functions are present in C

  1. Library Functions:

Library functions are the in-built functions which are declared in header files like printf(),scanf(),puts(),gets() etc.,

  1. User defined functions:

User defined functions are the ones which are written by the programmer based on the requirement.

How to declare a Function

return_type function_name(parameters);

How to call a Function

function_name (parameters)

How to define a Function

return_type function_name(parameters) {  
  //code
}