DATA STRUCTURES PROGRAM • STACKS & EXPRESSIONS

Implement a Stack Using a Linked List

Learn how to implement a stack using a linked list using a clear C program.

BeginnerStackLIFOpush/pop

PROBLEM UNDERSTANDING

Input and expected output

Sample input

No input required

Sample output

Popped = 30
Top = 20

COMPLETE C PROGRAM

Complete C implementation

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

struct Node { int data; struct Node *next; };
void push(struct Node **top, int value)
{
    struct Node *node = malloc(sizeof *node);
    if (node == NULL) exit(EXIT_FAILURE);
    node->data = value; node->next = *top; *top = node;
}
int pop(struct Node **top)
{
    if (*top == NULL) { puts("Stack underflow."); exit(EXIT_FAILURE); }
    struct Node *removed = *top; int value = removed->data;
    *top = removed->next; free(removed); return value;
}

int main(void)
{
    struct Node *top = NULL;
    push(&top, 10); push(&top, 20); push(&top, 30);
    printf("Popped = %d\n", pop(&top));
    printf("Top = %d\n", top->data);
    while (top != NULL) pop(&top);
    return 0;
}

CURRENT STEP

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EXPECTED OUTPUT FOR THE SAMPLE

Popped = 30
Top = 20

0%Step 0 of 0

PROGRAM EXPLANATION

Algorithm and explanation

Read the required input values.
Treat the list head as the stack top for constant-time insertion and deletion.
Display the computed result.

Treat the list head as the stack top for constant-time insertion and deletion.

EFFICIENCY

Time and space complexity

Time complexity

O(1) per operation

Auxiliary space

O(n)

DEBUGGING CHECKLIST

Common mistakes

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Use the correct format specifier for every variable.

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Initialize variables before using their values.

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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.