C++ Stack Exercises: K^th element of a stack from top position

C++ Stack: Exercise-14 with Solution

Write a C++ program to get the K^th element of a stack from top position.

Test Data:
Input some elements onto the stack:
Stack elements are: 4 3 2 1
Remove 2 from the said stack:
2nd element from the top of the stack: 3

Sample Solution:

C++ Code:

#include <iostream>

using namespace std;
#define MAX_SIZE 15 // Maximum size of stack
class Stack {
private:
    int top; // Index of top element
    int arr[MAX_SIZE]; // Array to store elements
public:
    Stack() {
        top = -1; // Initialize top index to -1 (empty stack)
    }

    bool push(int x) {
        if (isFull()) {
            cout << "Stack is full!" << endl;
            return false;
        }
        // Increment top index and add element to array
        arr[++top] = x; 
        return true;
    }

    int pop() {
        if (isEmpty()) {
            cout << "Stack underflow" << endl;
            return 0;
        }
        // Return top element and decrement top index
        return arr[top--]; 
    }

    int peek() {
        if (isEmpty()) {
            cout << "Stack is empty" << endl;
            return 0;
        }
        // Return top element without modifying top index
        return arr[top]; 
    }

    bool isEmpty() {
    	// Stack is empty if top index is -1
        return (top < 0); 
    }

    bool isFull() {
    	// Stack is full if top index is equal to MAX_SIZE - 1
        return (top >= MAX_SIZE - 1); 
    }

    void display() {
        if (top < 0) {
            cout << "Stack is empty" << endl;
            return;
        }
        cout << "\nStack elements are: ";
        for (int i = top; i >= 0; i--)
            cout << arr[i] << " ";
        cout << endl;
    }  
int getSize() {
      return top + 1;
    }       
int get_Kth_element_from_top(Stack& stk, int k) {
    if (stk.isEmpty()) {
        cout << "Stack is empty." << endl;
        return -1;
    }
    if (k < 1 || k > stk.getSize()) {
        cout << "Invalid k value." << endl;
        return -1;
    }
    int size = stk.getSize();
    int temp[size];
    int count = 0;
    // Copy stack elements into a temporary array
    while (!stk.isEmpty()) {
        temp[count++] = stk.pop();
    }
    // Get kth element from top of stack
    int kthElement = temp[k-1]; 
    // Place elements back in their original order on the stack
    for (int i = count-1; i >= 0; i--) {
        stk.push(temp[i]);
    }
    return kthElement;
}
};
int main() {
    Stack stk; 
    cout << "Input some elements onto the stack:";
    stk.push(1);
    stk.push(2);
    stk.push(3);
    stk.push(4);
    stk.display();
    cout << "\nRemove 2 from the said stack:";
    int z = stk.get_Kth_element_from_top(stk, 2);
	cout << "\n2nd element from the top of the stack: " << z;
	cout << "\n\nInput two more elements onto the stack:";
    stk.push(-1);
    stk.push(0);
    stk.display();
	z = stk.get_Kth_element_from_top(stk, 1);
	cout << "\n1st element from the top of the stack: " << z;
	z = stk.get_Kth_element_from_top(stk, 3);
	cout << "\n3rd element from the top of the stack: " << z;
	z = stk.get_Kth_element_from_top(stk, 6);
	cout << "\n6th element from the top of the stack: " << z;
    cout << endl;
}

Sample Output:

Input some elements onto the stack:
Stack elements are: 4 3 2 1

Remove 2 from the said stack:
2nd element from the top of the stack: 3

Input two more elements onto the stack:
Stack elements are: 0 -1 4 3 2 1

1st element from the top of the stack: 0
3rd element from the top of the stack: 4
6th element from the top of the stack: 1

Flowchart:

CPP Code Editor:

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