《Java数据结构与算法》笔记-CH5-链表-2单链表，增加根据关键字查找和删除

/**
 * Link节点 有数据项和next指向下一个Link引用
 */
class Link {
	private int iData;// 数据
	private double dData;// 数据
	public Link next;// 下一个link节点的引用

	public int getiData() {
		return iData;
	}

	public Link(int i, double d) {
		iData = i;
		dData = d;
	}

	public String toString() {
		return "[" + iData + "," + dData + "]";
	}

	public void displayLink() {
		System.out.println(toString());
	}
}

/**
 * 链表类 维护一个头节点
 */
class LinkList {
	private Link first;

	/**
	 * 初始化的时候头结点置空
	 */
	public LinkList() {
		first = null;
	}

	/**
	 * 头结点是空代表链表为空
	 * 
	 * @return
	 */
	public boolean isEmpty() {
		return first == null;
	}

	/**
	 * 向链表头插入Link节点
	 * 
	 * @param link
	 */
	public void insertFirst(Link link) {
		link.next = first;// 要插入的节点的next指针指向链表的头节点
		first = link;// 链表的头结点指向被插入的节点
	}

	/**
	 * 从链表头删除头结点并返回
	 * 
	 * @return
	 */
	public Link deleteFirst() {
		Link temp = first;// temp临时存上头结点
		first = first.next;// 将头节点的next指针指向下一个节点
		return temp;// 返回temp
	}

	@Override
	public String toString() {
		if (isEmpty())
			return "{}";
		StringBuilder sb = new StringBuilder();
		sb.append("{");
		Link current = first;
		while (current != null) {
			sb.append(current.toString());
			sb.append(",");
			current = current.next;
		}
		sb.deleteCharAt(sb.length() - 1);
		sb.append("}");
		return sb.toString();
	}

	/**
	 * 根据key寻找节点
	 * 
	 * @param key
	 * @return
	 */
	public Link find(int key) {
		Link curr = first;
		while (curr.getiData() != key) {
			if (curr.next == null)
				return null;
			else
				curr = curr.next;
		}
		return curr;
	}

	/**
	 * 根据key值删除节点
	 * 
	 * @param key
	 * @return
	 */
	public Link deleteByKey(int key) {
		Link current = first;
		Link previous = first;
		// 根据key值遍历
		while (current.getiData() != key) {
			if (current.next == null)//找不到，返回null
				return null;
			else {
				previous = current;
				current = current.next;
			}
		}
		//找到，此时头结点就是要删除的节点，直接把头结点置为头结点的next节点
		if (current == first)
			first = first.next;
		else//找到，此时把前一个节点的next指向当前节点的next即可
			previous.next = current.next;
		return current;
	}

	public void displayList() {
		System.out.println(toString());
	}
}

public class LinkListDemo {
	public static void main(String[] args) {
		LinkList ll = new LinkList();
		for (int i = 0; i < 10; i++) {
			Link l = new Link(i, i + 11.23);
			ll.insertFirst(l);
			ll.displayList();
		}
		ll.deleteFirst();
		ll.deleteFirst();
		ll.displayList();
		Link l3 = ll.find(3);
		System.out.println("key 为3的节点是: "+l3.toString());
		ll.deleteByKey(3);
		System.out.print("删除该节点后，链表是：");
		ll.displayList();
	}
}