CareerCup_3.3 - SetOfStacks

node.java

package Chapter3;

public class Node<T> {
    public T value;
    public Node<T> next;
    
    public Node(T d, Node<T> n){
   	value = d;
   	next = n;
    }
}

SetOfStacks.java

package Chapter3;

import java.util.ArrayList;
import java.util.List;

public class SetOfStacks<T> {
    private List<Stack<T>> stacks;
    private int capacity;

    public SetOfStacks(int c) {
	stacks = new ArrayList<Stack<T>>();
	capacity = c;
    }

    // go through all stacks and return size
    public int size() {
	int sz = 0;
	for (int i = 0; i < stacks.size(); i++) {
	    sz += stacks.get(i).size();
	}
	return sz;
    }

    public void push(T value) {
	if (stacks.size() == 0
		|| stacks.get(stacks.size() - 1).size() >= capacity) {
	    // add one more stack if the current stack is full
	    stacks.add(new Stack<T>());
	}
	stacks.get(stacks.size() - 1).push(value);
    }

    public T pop() {
	if (stacks.size() == 0)
	    return null;
	Stack<T> s = stacks.get(stacks.size() - 1);
	T res = s.pop();
	// remove current stack if it's empty
	if (s.size() == 0)
	    stacks.remove(stacks.size() - 1);
	return res;
    }

    // simply pop that stack
    // without fill in the empty space from the bottom of following stacks
    public T popAt(int index) {
	if (index >= stacks.size())
	    return null;
	Stack<T> s = stacks.get(index);
	T res = s.pop();
	if (s.size() == 0)
	    stacks.remove(index);
	return res;
    }

    public void printAll() {
	for (int i = 0; i < stacks.size(); i++) {
	    Stack<T> s = stacks.get(i);
	    s.print();
	}
    }

    public static void main(String[] args) {
	SetOfStacks<Integer> setOfStacks = new SetOfStacks<>(5);
	for (int i = 1; i <= 20; i++) {
	    setOfStacks.push(i);
	}

	for (int i = 1; i <= 5; i++) {
	    setOfStacks.pop();
	}

	setOfStacks.popAt(1);

	setOfStacks.printAll();
	System.out.println("Size after operations: " + setOfStacks.size());
    }
}

Stack.java

package Chapter3;

public class Stack<T> {
    private int size = 0;
    public Node<T> top = null;

    public int size() {
	return size;
    }

    public boolean isEmpty() {
	return size == 0;
    }

    public void push(T value) {
	Node<T> n = new Node<T>(value, top);
	size++;
	top = n;
    }

    public T pop() {
	if (top == null)
	    return null;
	T res = top.value;
	top = top.next;
	size--;
	return res;
    }

    public void print() {
	if(top == null) return;
	Node<T> cur = top;
	while(cur != null) {
	    System.out.print(cur.value + "; ");
	    cur = cur.next;
	}
	System.out.println();
    }
}