/* File: StackLL.java
 * Author: Wayne Snyder (waysnyder@gmail.com)
 * Data: Jul 29, 2020
 * Purpose: Example of Deque implemented by Doubly-Linked List
 */
import java.util.Arrays;

public class StackLL {

    private class Node {
        int item;
        Node next;
        public Node(int i, Node n) {
            item = i; next = n;
        }
    }

    private Node top = null;
    private int size = 0;

    // put a new int on top of the stack
    public void push(int i) {
        top = new Node(i,top);
        ++size;
    }


    // remove top int from the stack and return it
    public int pop() {
        int n = top.item;
        top = top.next;
        --size;
        return n;
    }

    // return top int without removing it
    public int top() {
        return top.item;
    }

    // number of ints in the stack
    public int size() {
        return size;
    }

    // is the stack empty?
    public boolean isEmpty() {
        return size == 0;

    }


    // just for debugging and tracing
    public String toString() {
        String s = "top-> ";
        for(Node p=top; p!=null; p=p.next) {
            s += p.item + " -> ";
        }
        return s + ".";
    }

    public static void main(String[] args) {

        System.out.println("\nUnit Test for Stack ADT");

        StackLL SLL = new StackLL();

        // test size and isEmpty on empty stack

        System.out.println("\nsize() => " + SLL.size());

        System.out.println("\nisEmpty() => " + SLL.isEmpty());

        System.out.println("\nPush 3, 6 and 7: ");
        SLL.push(3);
        SLL.push(6);
        SLL.push(7);

        System.out.println();
        System.out.println(SLL);

        System.out.println("\nsize() => " + SLL.size());

        System.out.println("\nisEmpty() => " + SLL.isEmpty());

        System.out.println("\npop() => " + SLL.pop());
        System.out.println("\npop() => " + SLL.pop());

        System.out.println("\nPush 7:");
        SLL.push(7);
        System.out.println();
        System.out.println(SLL);

        System.out.println("\nsize() => " + SLL.size());

        System.out.println("\nisEmpty() => " + SLL.isEmpty());

        //  Now test resizing

        for(int i = 9; i<100; i += 2) {
            SLL.push(i);
        }

        System.out.println();
        System.out.println(SLL);

        while(!SLL.isEmpty()) {
            SLL.pop();
        }

        System.out.println();
        System.out.println(SLL);

        System.out.println("\nsize() => " + SLL.size());

        System.out.println("\nisEmpty() => " + SLL.isEmpty());

    }
}