C++ Stack Exercises: Replace the kth 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-stack-exercise-flowchart-15-1
CPP Code Editor:
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Previous C++ Exercise: Kth element of a stack from top position.
Next C++ Exercise: Implement a stack using a linked list with push, pop.
What is the difficulty level of this exercise?
C++ Programming: Tips of the Day
Can you remove elements from a std::list while iterating through it?
You have to increment the iterator first (with i++) and then remove the previous element (e.g., by using the returned value from i++). You can change the code to a while loop like so:
std::list<item*>::iteratori = items.begin(); while (i != items.end()) { boolisActive = (*i)->update(); if (!isActive) { items.erase(i++); // alternatively, i = items.erase(i); } else { other_code_involving(*i); ++i; } }
Ref : https://bit.ly/3smQY4u
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