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 to store elements	
   vector<int> elements; 

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

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

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

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

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

vector<int> getMiddleElements() {
    vector<int> result;
    int size = elements.size();
    if (size % 2 == 0) {
        result.push_back(elements[size/2 - 1]);
    }
    result.push_back(elements[size/2]);
    return result;
  }
};  

int main() {
    Stack stack;
    //Initialize a stack 
    cout << "Create a stack object:\n";
    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] << " ";
    }
    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] << " ";
    }
    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:

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Previous C++ Exercise: Reverse a stack (using a vector) elements.
Next C++ Exercise: Implement a stack using a Deque with push, pop operations.