﻿ C++ Find the middle element(s) of a stack (using a vector)

# C++ Stack Exercises: Find the middle element(s) of a stack (using a vector)

## C++ Stack: Exercise-27 with Solution

Write a C++ program to find the middle element(s) of a stack (using a vector).

Test Data:
Create a stack object:
Input and store (using vector) some elements onto the stack:
Stack elements are: 1 3 2 6 5 -1
Middle element(s) of the said stack elements:
2 6

Sample Solution:

C++ Code:

``````#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

class Stack {
private:
vector<int> elements; // Vector to store elements

public:
void push(int element) {
elements.push_back(element); // Add element to the end of the vector
}

void pop() {
if (elements.empty()) {
cout << "Stack is full" << endl; // Display full message if the stack is empty
} else {
elements.pop_back(); // Remove the last element from the vector
}
}

int top() {
if (elements.empty()) {
cout << "Stack is empty" << endl; // Display empty message if the stack is empty
return 0;
} else {
return elements.back(); // Return the last element in the vector
}
}

bool empty() {
return elements.empty(); // Check if the vector is empty
}

void display() {
vector<int> v = elements;
if (v.empty()) {
cout << "Stack is empty" << endl; // Display empty message if the stack is empty
return;
}
cout << "Stack elements are: ";
for (int i = 0; i < v.size(); i++) {
cout << v[i] << " "; // Display the elements of the stack
}
cout << endl;
}

// Function to get the middle element(s) of the stack
vector<int> getMiddleElements() {
vector<int> result;
int size = elements.size();
if (size % 2 == 0) {
result.push_back(elements[size / 2 - 1]); // Add middle element if stack size is even
}
result.push_back(elements[size / 2]); // Add middle element if stack size is odd
return result;
}
};

int main() {
Stack stack;
cout << "Create a stack object:\n"; // Initialize a stack
cout << "\nInput and store (using vector) some elements onto the stack:\n";
stack.push(1);
stack.push(3);
stack.push(2);
stack.push(6);
stack.push(5);
stack.push(-1);
stack.display();
cout << "\nMiddle element(s) of the said stack elements:\n";
vector<int> middleElements = stack.getMiddleElements();
for (int i = 0; i < middleElements.size(); i++) {
cout << middleElements[i] << " "; // Display middle element(s)
}
cout << "\n\nInput one more element:\n";
stack.push(0);
stack.display();
cout << "\nMiddle element(s) of the said stack elements:\n";
middleElements = stack.getMiddleElements();
for (int i = 0; i < middleElements.size(); i++) {
cout << middleElements[i] << " "; // Display middle element(s)
}
cout << endl;
return 0;
}
``````

Sample Output:

```Create a stack object:

Input and store (using vector) some elements onto the stack:
Stack elements are: 1 3 2 6 5 -1

Middle element(s) of the said stack elements:
2 6

Input one more element:
Stack elements are: 1 3 2 6 5 -1 0

Middle element(s) of the said stack elements:
6
```

Flowchart:

CPP Code Editor: