DATA STRUCTURES PROGRAM • SINGLY LINKED LISTS

Delete the First Node of a Singly Linked List

Learn how to delete the first node of a singly linked list using a clear C program.

BeginnerLinked listNodePointers

PROBLEM UNDERSTANDING

Input and expected output

Sample input

No input required

Sample output

20 30

COMPLETE C PROGRAM

Complete C implementation

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

struct Node { int data; struct Node *next; };

struct Node *create_node(int value)
{
    struct Node *node = malloc(sizeof *node);
    if (node == NULL) { perror("malloc"); exit(EXIT_FAILURE); }
    node->data = value;
    node->next = NULL;
    return node;
}

void append(struct Node **head, int value)
{
    struct Node *node = create_node(value);
    if (*head == NULL) { *head = node; return; }
    struct Node *current = *head;
    while (current->next != NULL) current = current->next;
    current->next = node;
}

void print_list(const struct Node *head)
{
    while (head != NULL) { printf("%d ", head->data); head = head->next; }
    putchar('\n');
}

void free_list(struct Node *head)
{
    while (head != NULL) { struct Node *next = head->next; free(head); head = next; }
}

int main(void)
{
    struct Node *head = NULL;
    append(&head, 10); append(&head, 20); append(&head, 30);
    if (head != NULL) { struct Node *removed = head; head = head->next; free(removed); }
    print_list(head);
    free_list(head);
    return 0;
}

CURRENT STEP

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SELECTED LINE

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EXPECTED OUTPUT FOR THE SAMPLE

20 30

0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

Read the required input values.
Save the current head, advance head to the second node and release the removed node.
Display the computed result.

Save the current head, advance head to the second node and release the removed node.

EFFICIENCY

Time and space complexity

Time complexity

O(1)

Auxiliary space

O(n)

DEBUGGING CHECKLIST

Common mistakes

Check this

Use the correct format specifier for every variable.

Check this

Initialize variables before using their values.

Check this

Check braces, semicolons and input order carefully.

Try it yourself

Practice: Run the program with the sample input, predict its output, and then test one boundary case of your own.