Java-DSA/_105queue2stack.java at main · AyanJaved/Java-DSA · GitHub

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import java.util.*;
public class _105queue2stack {
    static class Stack{
        static Queue<Integer> q1 = new LinkedList<>();
        static Queue<Integer> q2 = new LinkedList<>();

        public static boolean isEmpty(){
            return q1.isEmpty() && q2.isEmpty();
        }
        public static void push(int data){
            if(!q1.isEmpty()){
                q1.add(data);
            } else{
                q2.add(data);
            }
        }
        public static int pop(){
            if(isEmpty()){
                System.out.println("Empty");
                return -1;
            }
            int top = -1;
            if(!q1.isEmpty()){
                while(!q1.isEmpty()){
                    top=q1.remove();
                    if(q1.isEmpty()){
                        break;
                    }
                    q2.add(top);
                }
            } else{
                while(!q2.isEmpty()){
                    top = q2.remove();
                    if(q2.isEmpty()){
                        break;
                    }
                    q1.add(top);
                }
            }
            return top;
        }
        public static int peek(){
            if(isEmpty()){
                System.out.println("Empty");
                return -1;
            }
            int top = -1;
            if(!q1.isEmpty()){
                while(!q1.isEmpty()){
                    top=q1.remove();
                    q2.add(top);
                }
            } else{
                while(!q2.isEmpty()){
                    top = q2.remove();
                    q1.add(top);
                }
            }
            return top;
        }
    }

    public static void main(String[] args) {
        Stack s = new Stack();
        s.push(1);
        s.push(2);
        s.push(3);
        while(!s.isEmpty()){
            System.out.println(s.peek());
            s.pop();
        }
    }
}