java 单链表 练习

练习一下java单链表的简单习题

package com.test1;

import java.util.Stack;

public class SingleListDemo {

	/**
	 * 返回单链表的总长度
	 * @param sl
	 * @return
	 */
	public static <T> int getListLength(SingleList<T> sl) {
		Node<T> temp = sl.headNode.next;
		int index = 0;
		while(temp != null) {
			temp = temp.next;
			index++;
		}
		return index;
	}

	/**
	 * 查找单链表中倒数第k个元素
	 * @param sl
	 * @param k
	 * @return
	 */
	public static <T> Node<T> getLastK(SingleList<T> sl, int k){
		int length = getListLength(sl);
		if(length < k) {
			throw new RuntimeException("不存在倒数第" + k + "个节点");
		}
		int index = length - k;
		Node<T> temp = sl.headNode.next;
		while(index != 0) {
			temp = temp.next;
			index--;
		}
		return temp;
	}

	/**
	 * 单链表的反转
	 * @param <T>
	 * @param args
	 */
	public static <T> void reverseList(SingleList<T> sl){
		int length = getListLength(sl);
		if(length == 1) {
			return;
		}

		Node<T> headNode = sl.headNode;
		Node<T> last =  headNode.next;
		Node<T> cur = last.next;
		Node<T> next = cur.next;
		last.next = null;
		while(next != null) {
			cur.next = last;
			last = cur;
			cur = next;
			next = next.next;
		}
		cur.next = last;
		sl.headNode.next = cur;
	}

	/**
	 * 从尾到头打印单链表 (利用栈)
	 * @param <T>
	 * @param args
	 */
	public static <T> void printReverseList1(SingleList<T> sl) {
		Node<T> temp = sl.headNode.next;
		Stack<T> stack = new Stack<>();
		while(temp != null) {
			stack.push(temp.data);
			temp = temp.next;
		}
		while(!stack.empty()) {
			System.out.println(stack.pop());
		}
	}

	/**
	 * 从尾到头打印单链表 (利用递归) 很是牛逼！
	 * @param <T>
	 * @param args
	 */
	public static <T> void printReverseList2(Node<T> node) {
		if(node.next != null) {
			printReverseList2(node.next);
		}
		System.out.println(node.data);
	}

	/**
	 * 合并两个有序的单链表，合并之后的单链表任然有序
	 * @param <T>
	 * @param args
	 */
	public static <T> SingleList<T> mergeTwoList(SingleList<T> sl1, SingleList<T> sl2) {
		SingleList<T> result = new SingleList<>();
		Node<T> temp1 = sl1.headNode.next;
		Node<T> temp2 = sl2.headNode.next;
		while(temp1 != null && temp2 != null) {
			if(temp1.compareTo(temp2) < 0) {
				Node<T> temp = temp1;
				temp1 = temp1.next;
				temp.next = null;
				result.addNode(temp);
			} else {
				Node<T> temp = temp2;
				temp2 = temp2.next;
				temp.next = null;
				result.addNode(temp);
			}
		}
		Node<T> temp = temp1 == null ? temp2 : temp1;
		while(temp != null) {
			result.addNode(temp);
			temp = temp.next;
		}
		return result;
	}

	public static void main(String[] args) {
//		SingleList<String> sl = new SingleList<>();
//		sl.addNode(new Node<>("李四", null));
//		sl.addNode(new Node<>("张三", null));
//		sl.addNode(new Node<>("王五", null));
//		sl.addNode(new Node<>("赵六", null));
//		sl.showData();
//		System.out.println(getListLength(sl));
//		Node<String> node = getLastK(sl, 2);
//		System.out.println(node);
//		reverseList(sl);
//		System.out.println("\n反转之后为：");
//		sl.showData();
//		System.out.println("\n从尾到头打印单链表");
//		printReverseList2(sl.headNode.next);
//		Node<Integer> a = new Node<>(1, null);
//		Node<Integer> b = new Node<>(2, null);
//		System.out.println(a.compareTo(b));

		SingleList<Integer> sl = new SingleList<>();
		sl.addNodeOrder(new Node<>(1, null));
		sl.addNodeOrder(new Node<>(3, null));
		sl.addNodeOrder(new Node<>(70, null));
		sl.addNodeOrder(new Node<>(2, null));
		sl.showData();
		SingleList<Integer> sl1 = new SingleList<>();
		sl1.addNodeOrder(new Node<>(11, null));
		sl1.addNodeOrder(new Node<>(13, null));
		sl1.addNodeOrder(new Node<>(17, null));
		sl1.addNodeOrder(new Node<>(12, null));
		sl1.showData();
		System.out.println("\n合并之后为：");
		SingleList<Integer> result = mergeTwoList(sl, sl1);
		result.showData();
	}
}

class Node<T> implements Comparable<Node<T>>{
	public T data;
	public Node<T> next;
	public Node(T data, Node<T> next) {
		super();
		this.data = data;
		this.next = next;
	}
	@Override
	public String toString() {
		return this.data.toString();
	}

	@SuppressWarnings("unchecked")
	@Override
	public int compareTo(Node<T> o) {
		if(o.data instanceof Comparable) {
			return ((Comparable<Comparable<?>>) this.data).compareTo((Comparable<?>) o.data);
		}
		return 0;
	}

}

class SingleList<T>{
	public Node<T> headNode = new Node<>(null, null);

	/**
	 * 往尾部添加节点
	 * @param node
	 */
	public void addNode(Node<T> node) {
		Node<T> temp = headNode;
		while(temp.next != null) {
			temp = temp.next;
		}
		temp.next = node;
	}

	/**
	 * 按照节点的大小添加节点，使得链表有序
	 */
	public void addNodeOrder(Node<T> node) {
		Node<T> last = headNode;
		Node<T> temp = last.next;
		while(temp != null && temp.compareTo(node) < 0) {
			last = temp;
			temp = temp.next;
		}
		if(temp != null && temp.compareTo(node) == 0) {
			throw new RuntimeException("已经存在相同的节点，不允许再次添加");
		}
		last.next = node;
		node.next = temp;
	}

	/**
	 * 显示list中的数据
	 */
	public void showData() {
		Node<T> temp = headNode.next;
		while(temp != null) {
			System.out.print(temp + " ");
			temp = temp.next;
		}
	}

}