DATA STRUCTURES PROGRAM • SINGLY LINKED LISTS

Search for a Value in a Singly Linked List

Learn how to search for a value in a singly linked list using a clear C program.

BeginnerLinked listNodePointers

PROBLEM UNDERSTANDING

Input and expected output

Sample input

No input required

Sample output

Found at position 2

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, 8); append(&head, 13); append(&head, 21);
    int key = 13, position = 1;
    const struct Node *current = head;
    while (current != NULL && current->data != key) { current = current->next; position++; }
    if (current != NULL) printf("Found at position %d\n", position);
    else puts("Value not found.");
    free_list(head);
    return 0;
}

CURRENT STEP

Select Start to walk through the important lines.

SELECTED LINE

No line selected

EXPECTED OUTPUT FOR THE SAMPLE

Found at position 2

0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

Read the required input values.
Traverse sequentially until the key matches or the end is reached.
Display the computed result.

Traverse sequentially until the key matches or the end is reached.

EFFICIENCY

Time and space complexity

Time complexity

O(n)

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.