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MyDeque.java
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114 lines (91 loc) · 2.56 KB
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public class MyDeque<E> {
private int size = 0;
private Node<E> first, rear = null;
public void addFirst(E e) {
Node<E> node = new Node<E>(e, null, first);
if(isEmpty()) {
first = rear = node;
} else {
first.pre = node;
first = node;
}
size++;
}
public void addLast(E e) {
Node<E> node = new Node<E>(e, rear, null);
if(isEmpty()) {
first = rear = node;
} else {
rear.next = node;
rear = node;
}
size++;
}
public E removeFirst() {
if(isEmpty())
return null;
size--;
Node<E> node = first;
first = node.next;
if(first != null) first.pre = null;
return node.item;
}
public E removeLast() {
if(isEmpty())
return null;
size--;
Node<E> node = rear;
rear = node.pre;
if(rear != null) rear.next = null;
return node.item;
}
public boolean isEmpty() {
return size == 0;
}
public int getSize() {
return size;
}
public void print() {
StringBuilder sb = new StringBuilder("[");
Node<E> node = first;
while(node != null) {
sb.append(node.item.toString());
if(node.next != null) sb.append(",");
node = node.next;
}
sb.append("]");
System.out.println(sb.toString());
}
private final static class Node<E> {
E item;
Node<E> pre, next;
Node(E item, Node<E> pre, Node<E> next) {
this.item = item;
this.pre = pre;
this.next = next;
}
}
public static void main(String[] args) {
MyDeque<Integer> deque = new MyDeque<Integer>();
deque.addFirst(1);
deque.addLast(2);
deque.addFirst(3);
deque.addLast(4);
deque.addFirst(5);
deque.addLast(6);
deque.print();
System.out.println("==============================================");
System.out.println("remove first: " + deque.removeFirst());
System.out.println("remove last: " + deque.removeLast());
deque.print();
System.out.println("==============================================");
deque.removeFirst();
deque.removeLast();
deque.removeLast();
deque.removeFirst();
deque.print();
System.out.println("==============================================");
deque.addFirst(10);
deque.print();
}
}