자바 알고리즘 정복 3 - 스택, 큐

# 제네릭 스택(연결리스트 활용)

package StudyJava.Stack;

import java.util.EmptyStackException;

public class GenericStack<T> {
    class Node<T> {
        private T data;
        private Node<T> next;

        public Node(T data) {
            this.data = data;
        }
    }

    private Node<T> top;

    public T pop() {
        if(top == null) {
            throw new EmptyStackException();
        }
        T item = top.data;
        top = top.next;
        return item;
    }

    public void push(T item) {
        Node<T> t = new Node<T>(item);
        t.next = top;
        top = t;
    }

    public T peek() {
        if(top == null) {
            throw new EmptyStackException();
        }
        return top.data;
    }

    public boolean isEmpty() {
        return top == null;
    }
}

 

# 제네릭 큐(연결리스트 활용)

class Queue<T> {

    class Node<T> {
        private T data;
        private Node<T> next;

        public Node(T data) {
            this.data = data;
        }
    }
    private Node<T> first;
    private Node<T> last;

    public void add(T item) {
        Node<T> t = new Node<T>(item);
        if(last != null) {
            last.next = t;
        }
        last = t;
        if(first == null) {
            first = last;
        }
    }

    public T remove() {
        if(first == null) {
            throw new NoSuchElementException();
        }

        T data = first.data;
        first = first.next;

        if(first == null) { // 큐가 비었을때
            last = null;
        }
        return data;
    }

    public T peek() {
        if(first == null) {
            throw new NoSuchElementException();
        }
        return first.data;
    }

    public boolean isEmpty() {
        return first == null;
    }
}