1.Stack
package algs4; import java.util.Iterator;
import java.util.NoSuchElementException; public class Stack<Item> implements Iterable<Item> { private Node<Item> first;
private int n; private static class Node<Item> {
private Item item;
private Node<Item> next;
} public Stack() {
first = null;
n = 0;
} public boolean isEmpty() {
return first == null;
} public int size() {
return n;
} public void push(Item item) {
Node<Item> oldfirst = first;
first = new Node<Item>();
first.item = item;
first.next = oldfirst;
n++;
} public Item pop() {
if (isEmpty()) throw new NoSuchElementException("Stack underflow");
Item item = first.item;
first = first.next;
n--;
return item; } public Item peek() {
if (isEmpty()) throw new NoSuchElementException("Stack underflow");
return first.item;
} public String toString() {
StringBuilder s = new StringBuilder();
for (Item item : this)
s.append(item + " ");
return s.toString();
} @Override
public Iterator<Item> iterator() {
// TODO Auto-generated method stub
return new ListIterator<Item>(first);
} private class ListIterator<Item> implements Iterator<Item> {
private Node<Item> current; public ListIterator(Node<Item> first) {
// TODO Auto-generated constructor stub
current = first;
} @Override
public boolean hasNext() {
// TODO Auto-generated method stub
return current != null;
} @Override
public Item next() {
// TODO Auto-generated method stub
if (!hasNext()) throw new NoSuchElementException();
Item item = current.item;
current = current.next;
return item;
} @Override
public void remove() {
// TODO Auto-generated method stub
throw new UnsupportedOperationException();
} } public static void main(String[] args) {
Stack<String> stack = new Stack<String>();
// while (!StdIn.isEmpty()) {
//
// }
} }
2.Queue
package algs4; import java.util.Iterator;
import java.util.NoSuchElementException; public class Queue<Item> implements Iterable<Item> {
private Node<Item> first;
private Node<Item> last;
private int n; private static class Node<Item> {
private Item item;
private Node<Item> next;
} public Queue() {
first = null;
last = null;
n = 0;
} public boolean isEmpty() {
return first == null;
} public int size() {
return n;
} public Item peek() {
if (isEmpty()) throw new NoSuchElementException("Stack underflow");
return first.item;
} public void enqueue(Item item) {
Node<Item> oldlast = last;
last = new Node<Item>();
last.item = item;
last.next = null;
if (isEmpty()) first = last;
else oldlast.next = last;
n++;
} public Item dequeue() {
if (isEmpty()) throw new NoSuchElementException("Stack underflow");
Item item = first.item;
first = first.next;
n--;
if (isEmpty()) last = null;
return item;
} public String toString() {
StringBuilder s = new StringBuilder();
for (Item item : this)
s.append(item + " ");
return s.toString();
} @Override
public Iterator<Item> iterator() {
// TODO Auto-generated method stub
return new ListIterator<Item>(first);
} private class ListIterator<Item> implements Iterator<Item> {
private Node<Item> current; public ListIterator(Node<Item> first) {
// TODO Auto-generated constructor stub
current = first;
} @Override
public boolean hasNext() {
// TODO Auto-generated method stub
return current != null;
} @Override
public Item next() {
// TODO Auto-generated method stub
if (!hasNext()) throw new NoSuchElementException();
Item item = current.item;
current = current.next;
return item;
} @Override
public void remove() {
// TODO Auto-generated method stub
throw new UnsupportedOperationException();
} }
}