Pop Using Linked List Node in DSA C - Build from Scratch

Pop Using Linked List Node

📖 Scenario: Imagine you have a stack of books represented as a linked list. You want to remove the top book from the stack and see which book was removed.

🎯 Goal: You will create a linked list representing a stack of books, then write code to remove (pop) the top book from the stack and print the remaining books.

📋 What You'll Learn

Create a linked list node structure with an integer data and a pointer to the next node called next.

Create a linked list with three nodes containing the values 10, 20, and 30, where 30 is the top of the stack.

Write a function called pop that removes the top node from the linked list and returns its value.

Print the linked list after popping the top node to show the remaining stack.

💡 Why This Matters

🌍 Real World

Stacks are used in many real-world applications like undo features in text editors, browser history, and expression evaluation.

💼 Career

Understanding linked list operations like pop is essential for software development roles involving data structures, memory management, and algorithm design.

1

Create the linked list nodes

Define a struct Node with an int data and a struct Node* next. Then create three nodes named node1, node2, and node3 with data 10, 20, and 30 respectively. Link them so that node3 points to node2, and node2 points to node1. Set head to node3.

DSA C

# Define struct Node and create three linked nodes
// Your code here

Hint

Remember to use malloc to create nodes and link them by setting the next pointer.

2

Create the pop function

Write a function called pop that takes a pointer to the pointer of the head node (struct Node** head). The function should remove the top node from the linked list, update the head to the next node, free the removed node, and return the removed node's data.

DSA C

#include 
#include 

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

int pop(struct Node** head) {
    // Remove the top node and return its data
    // Your code here
}

int main() {
    struct Node* node1 = (struct Node*)malloc(sizeof(struct Node));
    struct Node* node2 = (struct Node*)malloc(sizeof(struct Node));
    struct Node* node3 = (struct Node*)malloc(sizeof(struct Node));

    node1->data = 10;
    node1->next = NULL;

    node2->data = 20;
    node2->next = node1;

    node3->data = 30;
    node3->next = node2;

    struct Node* head = node3;

    return 0;
}

Hint

Use a temporary pointer to hold the top node, update the head to the next node, free the old top node, and return its data.

3

Pop the top node from the stack

In main, call the pop function with the address of head and store the returned value in an int popped_value variable.

DSA C

#include 
#include 

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

int pop(struct Node** head) {
    if (*head == NULL) {
        return -1; // Return -1 if stack is empty
    }
    struct Node* temp = *head;
    int popped_data = temp->data;
    *head = temp->next;
    free(temp);
    return popped_data;
}

int main() {
    struct Node* node1 = (struct Node*)malloc(sizeof(struct Node));
    struct Node* node2 = (struct Node*)malloc(sizeof(struct Node));
    struct Node* node3 = (struct Node*)malloc(sizeof(struct Node));

    node1->data = 10;
    node1->next = NULL;

    node2->data = 20;
    node2->next = node1;

    node3->data = 30;
    node3->next = node2;

    struct Node* head = node3;

    // Call pop and store the popped value
    // Your code here

    return 0;
}

Hint

Call pop with &head and save the result in popped_value.

4

Print the remaining stack after pop

Write a while loop to print the data of each node in the linked list starting from head. Print each value followed by -> . After the loop, print null to show the end of the list. Also, print the popped value with the message Popped value: .

DSA C

#include 
#include 

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

int pop(struct Node** head) {
    if (*head == NULL) {
        return -1; // Return -1 if stack is empty
    }
    struct Node* temp = *head;
    int popped_data = temp->data;
    *head = temp->next;
    free(temp);
    return popped_data;
}

int main() {
    struct Node* node1 = (struct Node*)malloc(sizeof(struct Node));
    struct Node* node2 = (struct Node*)malloc(sizeof(struct Node));
    struct Node* node3 = (struct Node*)malloc(sizeof(struct Node));

    node1->data = 10;
    node1->next = NULL;

    node2->data = 20;
    node2->next = node1;

    node3->data = 30;
    node3->next = node2;

    struct Node* head = node3;

    int popped_value = pop(&head);

    // Print the popped value and remaining stack
    // Your code here

    return 0;
}

Hint

Use a while loop to print each node's data followed by -> . After the loop, print null. Also print the popped value before the list.