C Exercises: Find the top and k^th element of a stack

Last update on March 20 2025 12:40:36 (UTC/GMT +8 hours)

16. Kth Element Retrieval in Stack

Write a C program to implement a stack and accept some numeric values. Find the top and k^th element of the stack.

Sample Solution:

C Code:

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

#define MAX_SIZE 100

// Declare the stack structure
struct Stack {
    int arr[MAX_SIZE]; // Array to store elements
    int top; // Index of the top element
};

// Initialize the stack
void init_Stack(struct Stack *stack) {
    stack->top = -1; // Initialize top index to -1
}

// Check if stack is empty
int isEmpty(struct Stack *stack) { 
    return (stack->top == -1); // Returns 1 if the stack is empty, 0 otherwise
}

// Check if stack is full
int isFull(struct Stack *stack) {
    return (stack->top == MAX_SIZE - 1); // Returns 1 if the stack is full, 0 otherwise
}

// Push an element to the stack
void push(struct Stack *stack, int value) {
    if (isFull(stack)) {
        printf("Stack is underflow!\n"); // Display an error message if the stack is full
        return;
    }
    stack->arr[++stack->top] = value; // Increment top index and add element
}

// Pop an element from the stack
int pop(struct Stack *stack) {
    if (isEmpty(stack)) {
        printf("Stack is empty!\n"); // Display an error message if the stack is empty
        return -1;
    }
    return stack->arr[stack->top--]; // Return top element and decrement top index
}

// Get the top element of the stack
int top(struct Stack *stack) {
    if (isEmpty(stack)) {
        printf("Stack is empty\n"); // Display an error message if the stack is empty
        return -1;
    }
    return stack->arr[stack->top]; // Return the top element of the stack
}

// Get the kth element from the top of the stack
int get_Kth_element_from_top(struct Stack *stack, int k) {
    if (k < 1 || k > stack->top + 1) {
        printf("Invalid value of k\n"); // Display an error message if k is out of range
        return -1;
    }
    return stack->arr[stack->top - k + 1]; // Return the kth element from the top of the stack
}

// Function to print the elements of the stack
void print_stack(struct Stack* s) {
    if (isEmpty(s)) {
        printf("Stack is empty\n"); // Display a message if the stack is empty
        return;
    }
    for (int i = 0; i <= s->top; i++) {
        printf("%d ", s->arr[i]); // Print each element of the stack
    }
    printf("\n");
}

// Main function
int main() {
    struct Stack stack;
    init_Stack(&stack); // Initialize the stack
    // Push elements onto the stack
    push(&stack, 1);
    push(&stack, 2);
    push(&stack, 3);
    push(&stack, 4);
    push(&stack, 5);
    push(&stack, 6);
    printf("Elements of the stack:\n");
    print_stack(&stack); // Print the elements of the stack
    printf("Top element: %d\n", top(&stack)); // Print the top element of the stack
    printf("3rd element from top: %d\n", get_Kth_element_from_top(&stack, 3)); // Print the 3rd element from the top
    printf("Remove the topmost element from the stack:\n");
    pop(&stack); // Remove the top element from the stack
    printf("Elements of the stack:\n");
    print_stack(&stack); // Print the elements of the stack after pop operation
    printf("Top element: %d\n", top(&stack)); // Print the top element of the stack
    printf("4th element from top: %d\n", get_Kth_element_from_top(&stack, 4)); // Print the 4th element from the top
    return 0;
}

Output:

Elements of the stack:
1 2 3 4 5 6
Top element: 6
3rd element from top: 4
Remove the topmost element from the stack:
Elements of the stack:
1 2 3 4 5
Top element: 5
4th element from top: 2 

Flowchart:

For more Practice: Solve these Related Problems:

• Write a C program to find the kth largest element in a stack without using sorting algorithms.
• Write a C program to retrieve both the kth element from the top and the kth element from the bottom of the stack.
• Write a C program to display the current top and kth element after every push or pop operation in a stack.
• Write a C program to swap the kth element from the top with the kth element from the bottom in a stack.

C Programming Code Editor:

Click to Open Editor

Have another way to solve this solution? Contribute your code (and comments) through Disqus.

Previous: Remove the minimum value from a stack.
Next: Decimal number to its binary equivalent using stack.