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

C++ Stack: Exercise-15 with Solution

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;
            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;
    }
    
    
void replaceKthPosition(Stack& stk, int k, int value) {
    if (stk.isEmpty()) {
        cout << "Stack is empty." << endl;
        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;
        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();
    cout << "\nReplace the kth element with new value:";
    int  k = 2, new_val = 14;
    cout << "\nk = " << k << " New val = " << new_val;
    stk.replaceKthPosition(stk, k, new_val);
    stk.display();
    cout << "\nReplace the kth element with new value:";
    k = 5, new_val = 56;
    cout << "\nk = " << k << " New val = " << 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:

CPP Code Editor:

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Previous C++ Exercise: K^th element of a stack from top position.
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