C++ Stack Exercises: Kth element of a stack from top position
C++ Stack: Exercise-14 with Solution
Write a C++ program to get the Kth 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:



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Previous C++ Exercise: Delete all occurrences of an item in a stack.
Next C++ Exercise: Replace the kth element with new value in a stack.
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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