Why Stack Exists and What Problems It Solves in DSA C - See It Work

Why Stack Exists and What Problems It Solves

📖 Scenario: Imagine you are organizing a stack of plates in a kitchen. You can only add or remove the top plate. This is how a stack data structure works in programming.Stacks help solve problems where the last thing added is the first thing you need to remove, like undo actions in text editors or checking if parentheses in math expressions are balanced.

🎯 Goal: You will create a simple stack using an array in C, push some numbers onto it, then pop them off to see how the last number added is the first one removed.

📋 What You'll Learn

Create an integer array called stack with size 5

Create an integer variable called top and set it to -1

Write a function push that adds a number to the stack and updates top

Write a function pop that removes and returns the top number from the stack and updates top

Push the numbers 10, 20, and 30 onto the stack

Pop all numbers from the stack and print them in order

💡 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 stacks is important for software developers to solve problems involving order and reversals, and is often asked in coding interviews.

1

Create the stack array and top variable

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

DSA C

# Create the stack array and top variable
// Your code here

Hint

Think of top as the position of the last added item. Starting at -1 means the stack is empty.

2

Write the push function

Write a function called push that takes an integer value, adds it to the stack at position top + 1, and updates top accordingly.

DSA C

int stack[5];
int top = -1;

// Write the push function below
// Your code here

Hint

Check if top is less than 4 before adding to avoid overflow.

3

Write the pop function

Write a function called pop that removes and returns the top value from the stack and updates top. If the stack is empty (top == -1), return -1.

DSA C

int stack[5];
int top = -1;

void push(int value) {
    if (top < 4) {
        top++;
        stack[top] = value;
    }
}

// Write the pop function below
// Your code here

Hint

Remember to decrease top after removing the top item.

4

Push and pop values, then print the popped values

Push the numbers 10, 20, and 30 onto the stack using push. Then pop all values from the stack using pop and print each popped value on a new line.

DSA C

int stack[5];
int top = -1;

void push(int value) {
    if (top < 4) {
        top++;
        stack[top] = value;
    }
}

int pop() {
    if (top == -1) {
        return -1;
    } else {
        int value = stack[top];
        top--;
        return value;
    }
}

int main() {
    // Push 10, 20, 30 onto the stack
    // Pop all values and print them
    // Your code here
    return 0;
}

Hint

Use a loop to pop until pop() returns -1, printing each value.