STL_Queue_Using_Stack.cpp

#include <iostream>
#include <stack>

using namespace std;
/*———————————————————————————————————————————————————————————————————————————*/
struct Queue{
    stack<int> s1, s2;
/*———————————————————————————————————————————————————————————————————————————*/
    void enQueue(int x){
        
        // Move all elements from s1 to s2
        while (!s1.empty()) {
            s2.push(s1.top());
            s1.pop();
        }

        // Push item into s1
        s1.push(x);

        // Push everything back to s1
        while (!s2.empty()) {
            s1.push(s2.top());
            s2.pop();
        }
        cout << x << " — EnQueued Successfully\n";
    }
/*———————————————————————————————————————————————————————————————————————————*/
    // Dequeue an item from the queue
    int deQueue(){
    
        // if first stack is empty
        if (s1.empty()) {
            cout << "Q is Empty";
            exit(0);
        }

        // Return top of s1
        int x = s1.top();
        s1.pop();
        cout << x << " — DeQueued Successfully\n";
        return x;
    }
/*———————————————————————————————————————————————————————————————————————————*/
    void display(){
        if (s1.empty()) {
            cout << "Queue is Empty\n";
            exit(0);
        }
    
        // Move all elements from s1 to s2
        while (!s1.empty()) {
            cout << s1.top() << " ";
            s2.push(s1.top());
            s1.pop();
        }

        // Push everything back to s1
        while (!s2.empty()) {
            s1.push(s2.top());
            s2.pop();
        }
       cout << endl;    
    }
};
/*———————————————————————————————————————————————————————————————————————————*/
// Driver code
int main(){
    Queue q;
    int elem;
    int num;
  
    do{        
        cout << "Enter \n1 ————> push\n2 ————> pop\n3 ————> display\n4 ————> exit\n";
        cout << "Please enter your choice : ";
        cin >> num;
        
        switch(num){
            
            case 1:
                cout << "\nEnter a Number : ";
                cin >> elem;
                q.enQueue(elem);
                break;
                
            case 2: 
                q.deQueue();
                break;
                 
            case 3: 
                cout << endl;
                q.display();
                break;
                
            case 4:
                break;
                 
            default : 
                cout << "Invalid Choice\n";
        }                   
        cout << endl;
      
    }while(num != 4);
    
  return 0;
}
/*———————————————————————————————————————————————————————————————————————————*/