Stack Concept and LIFO Principle in DSA C - Build from Scratch

Stack Concept and LIFO Principle

📖 Scenario: Imagine you have a stack of plates in your kitchen. You can only add a plate on top or remove the top plate. This is called Last In, First Out (LIFO) principle.We will create a simple stack using an array in C to understand how this works.

🎯 Goal: Build a simple stack in C that can hold 5 integer plates, add plates to the stack, and then remove the top plate to see the LIFO principle in action.

📋 What You'll Learn

Create an integer array called stack with size 5

Create an integer variable called top initialized to -1 to track the top of the stack

Write code to push three plates with values 10, 20, and 30 onto the stack

Write code to pop the top plate from the stack

Print the stack contents after the pop operation

💡 Why This Matters

🌍 Real World

Stacks are used in many places like undo features in apps, browser history, and managing function calls in programs.

💼 Career

Understanding stacks and LIFO is essential for software developers, especially when working with recursion, parsing, and memory management.

1

Create the stack array and top variable

Create an integer array called stack with size 5 and an integer variable called top initialized to -1.

DSA C

int stack[5];
int top = -1;
// Your code here

Hint

The stack array holds the plates. The top variable shows the index of the top plate. Start with -1 because the stack is empty.

2

Push three plates onto the stack

Add code to push three plates with values 10, 20, and 30 onto the stack by incrementing top and assigning the values to stack[top].

DSA C

int stack[5];
int top = -1;
// Push 10
// Push 20
// Push 30

Hint

To push a plate, increase top by 1, then put the plate value at stack[top].

3

Pop the top plate from the stack

Add code to pop the top plate by printing stack[top] and then decrementing top by 1.

DSA C

int stack[5];
int top = -1;
top++;
stack[top] = 10;
top++;
stack[top] = 20;
top++;
stack[top] = 30;
// Pop the top plate

Hint

To pop, print the top plate value, then decrease top by 1 to remove it from the stack.

4

Print the stack contents after pop

Use a for loop with variable i from 0 to top to print each plate value in stack[i] separated by spaces.

DSA C

int stack[5];
int top = -1;
top++;
stack[top] = 10;
top++;
stack[top] = 20;
top++;
stack[top] = 30;
printf("Popped plate: %d\n", stack[top]);
top--;
// Print stack contents after pop

Hint

Loop from 0 to top and print each plate value with a space. This shows the stack after popping the top plate.