C++ Stack Exercises: Replace the k^th element with new value in a stack

Last update on December 20 2024 12:25:36 (UTC/GMT +8 hours)

Write a C++ program to replace the kth element with new value in a stack (using an array).

Test Data:
Input some elements onto the stack:
Stack elements are: 5 2 2 4 7
Replace the kth element with new value:
k = 2 New val = 14

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; // Display message if stack is full
            return false; // Return false to indicate failure in pushing element
        }
        // Increment top index and add element to array
        arr[++top] = x; 
        return true; // Return true to indicate successful element addition
    }

    int pop() {
        if (isEmpty()) {
            cout << "Stack underflow" << endl; // Display message if stack is empty
            return 0; // Return 0 to indicate failure in popping element
        }
        // Return top element and decrement top index
        return arr[top--]; 
    }

    int peek() {
        if (isEmpty()) {
            cout << "Stack is empty" << endl; // Display message if stack is empty
            return 0; // Return 0 to indicate failure in peeking element
        }
        // 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; // Display message if stack is empty
            return;
        }
        cout << "\nStack elements are: ";
        for (int i = top; i >= 0; i--)
            cout << arr[i] << " "; // Display elements of the stack
        cout << endl;
    }

    void replaceKthPosition(Stack& stk, int k, int value) {
        if (stk.isEmpty()) {
            cout << "Stack is empty." << endl; // Display message if the stack is empty
            return;
        }

        int size = stk.top + 1;
        int temp[size];
        int count = 0;

        // The stack elements are copied into a temporary array
        while (!stk.isEmpty()) {
            temp[count++] = stk.pop();
        }

        // Replace the kth element in the temporary array
        if (k > count || k <= 0) {
            cout << "Invalid position." << endl; // Display message for an invalid position
            return;
        } else {
            temp[k - 1] = value;
        }

        // The elements are pushed back into the stack in reverse order
        for (int i = count - 1; i >= 0; i--) {
            stk.push(temp[i]);
        }
    }
};

int main() {
    Stack stk; 
    cout << "Input some elements onto the stack:";
    stk.push(7);
    stk.push(4);
    stk.push(2);
    stk.push(2);
    stk.push(5);
    stk.display();

    // Replace the kth element with new value
    int k = 2, new_val = 14;
    cout << "\nReplace the " << k << "th element with new value: " << new_val;
    stk.replaceKthPosition(stk, k, new_val);
    stk.display();

    // Replace another kth element with a different new value
    k = 5, new_val = 56;
    cout << "\nReplace the " << k << "th element with new value: " << new_val;
    stk.replaceKthPosition(stk, k, new_val);
    stk.display();
    cout << endl;
}

Sample Output:

Input some elements onto the stack:
Stack elements are: 5 2 2 4 7

Replace the kth element with new value:
k = 2 New val = 14
Stack elements are: 5 14 2 4 7

Replace the kth element with new value:
k = 5 New val = 56
Stack elements are: 5 14 2 4 56

Flowchart: