Question

In C++

Implement a queue data structure using two stacks. Remember a queue has enqueue and dequeue functions.

You could use either the array or linked list implementation for stacks and queues.

Source for stack array:

---------------------------------------------------

#include<iostream>
#define SIZE 100
#define NO_ELEMENT -999999
using namespace std;

class Stack {
int arr[SIZE]; // array to store Stack elements
int top;
public:
Stack() {
top = -1;
}

void push(int); // push an element into Stack
int pop(); // pop the top element from Stack
int topElement(); // get the top element
void display(); // display Stack elements from top to bottom
};

void Stack :: push(int data) {
//if stack is full tell the user sorry it is full
if (top == SIZE-1) {
cout << "Sorry, the stack is full" << endl;
} else {
top++;
arr[top] = data;
}
}

int Stack :: pop() {
//if stack is empty tell the user sorry it is empty
if (top == -1) {
cout << "Sorry, the stack is empty" << endl;
return NO_ELEMENT;
}
int val = arr[top];
top--;
return val;
}

int Stack :: topElement() {
//if stack is empty tell the user no it is empty
if (top == -1) {
cout << "Sorry, the stack is empty" << endl;
return NO_ELEMENT;
}
return arr[top];
}

void Stack :: display() {
cout << "Stack display:" << endl;
for (int i = top ; i >=0 ; i--) {
cout << arr[i] << endl;
}
}

int main() {
Stack s;
s.push(12);
s.push(5);
s.push(13);
s.display();
cout << "Top Element : " << s.topElement() << endl;
s.pop();
s.push(7);
s.display();
return 0;
}

Answer 1

#include <iostream>

#define SIZE 100

#define NO_ELEMENT -999999

using namespace std;

class Stack {

int arr[SIZE]; // array to store Stack elements

int top;

public:

Stack() {

top = -1;

}

void push(int); // push an element into Stack

int pop(); // pop the top element from Stack

int topElement(); // get the top element

void display(); // display Stack elements from top to bottom

int isEmpty();

};

void Stack :: push(int data) {

//if stack is full tell the user sorry it is full

if (top == SIZE-1) {

cout << "Sorry, the stack is full" << endl;

} else {

top++;

arr[top] = data;

}

}

int Stack :: isEmpty() {

return top==-1;

}

int Stack :: pop() {

//if stack is empty tell the user sorry it is empty

if (top == -1) {

cout << "Sorry, the stack is empty" << endl;

return NO_ELEMENT;

}

int val = arr[top];

top--;

return val;

}

int Stack :: topElement() {

//if stack is empty tell the user no it is empty

if (top == -1) {

cout << "Sorry, the stack is empty" << endl;

return NO_ELEMENT;

}

return arr[top];

}

void Stack :: display() {

cout << "Stack display:" << endl;

for (int i = top ; i >=0 ; i--) {

cout << arr[i] << endl;

}

}

struct Queue {

Stack stack1, stack2;

void enQueue(int x)

{

while (!stack1.isEmpty()) {

stack2.push(stack1.pop());

}

stack1.push(x);

while (!stack2.isEmpty()) {

stack1.push(stack2.pop());

}

}

int deQueue()

{

if (stack1.isEmpty()) {

cout << "Queue is Empty";

return -1;

}

int x = stack1.pop();

return x;

}

};

int main()

{

Queue q;

q.enQueue(10);

q.enQueue(22);

q.enQueue(45);

cout << q.deQueue() <<endl;

cout << q.deQueue() << endl;

return 0;

}

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SEE OUTPUT


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