队列：链表

什么是单链表：

由一串对象连接起来形成的表

单链表

1. 创建一个节点类Node.class
2. 存放所需要的属性数据和next(下一个对象)
3. 创建一个节点管理器来连接和管理节点ManageNode.class
4. 该管理器中初始化一个头节点不存放任何数据
5. 增加添加节点、修改节点、删除节点、打印节点的方法

code

package com.lemon.singlelinklist;

//管理节点
public class SingleLinkListManage {
	private Node headNode = new Node(0, "");

	// 添加数据
	public void addNode(Node node) {
		Node temp = headNode;
		while (true) {
			if (temp.next == null) {
				break;
			}
			temp = temp.next;
		}
		temp.next = node;
	}

	//有序添加
	public void orderAddNode(Node node) {
		Node temp = headNode;
		boolean flag = true;
		while(true) {
			if(temp.next == null) {
				break;
			}
			if(temp.next.id > node.id) {
				if(temp.next.id == node.id) {
					flag = false;
				}
				break;
			}
			temp = temp.next;
		}
		if(flag) {
			node.next = temp.next;
			temp.next = node;
		}
	}
	
	// 打印数据
	public void printSingleLinkList() {
		Node temp = headNode;
		if (temp.next == null) {
			System.err.println("链表为空");
		}
		temp = temp.next;
		while (true) {
			if (temp == null) {
				break;
			}
			System.out.println(temp.id + "\t" + temp.name);
			temp = temp.next;
		}
	}
	
	//修改数据
	public void reviseNodeName(Node node) {
		Node temp = headNode.next;
		while(true) {
			if(temp == null) {
				break;
			}
			if(temp.id == node.id) {
				temp.name = node.name;
				break;
			}
			temp = temp.next;
		}
	}
	
	//删除数据
	public void deleteNode(int id) {
		Node temp = headNode;
		while(true) {
			if(temp == null) {
				break;
			}
			if(temp.next.id == id) {
				temp.next = temp.next.next;
				break;
			}
			temp = temp.next;
		}
	}
}
//节点
class Node {
	int id;
	String name;
	Node next;

	public Node(int id, String name) {
		this.id = id;
		this.name = name;
		next = null;
	}

	@Override
	public String toString() {
		return "Node [id=" + id + ", name=" + name + "]";
	}
}

package com.lemon.singlelinklist;

public class Test01 {
	public static void main(String[] args) {
		Node node1 = new Node(1, "q");
		Node node2 = new Node(2, "w");
		Node node3 = new Node(3, "e");
		
		SingleLinkListManage manage = new SingleLinkListManage();
		manage.addNode(node1);
		manage.addNode(node3);
		manage.addNode(node2);
		
		manage.printSingleLinkList();
	}
}

关于单链表的面试题

1. 求单链表中有效节点的个数

package com.lemon.singlelinklist;

public class Test02 {
	public static void main(String[] args) {
		Node node1 = new Node(1, "q");
		Node node2 = new Node(2, "w");
		Node node3 = new Node(3, "e");
		Node node4 = new Node(2, "f");
		
		SingleLinkListManage manage = new SingleLinkListManage();
		manage.addNode(node1);
		manage.addNode(node2);
		manage.addNode(node3);
		System.out.println(getLength(manage.headNode));
	}
	
	public static int getLength(Node node) {
		if(node.next == null) {
			return 0;
		}
		int length = 0;
		while(node.next != null) {
			length++;
			node = node.next;
		}
		return length;
	}
}

2. 查找单链表中的倒数第k个节点

package com.lemon.singlelinklist;

public class Test02 {
	public static void main(String[] args) {
		Node node1 = new Node(1, "q");
		Node node2 = new Node(2, "w");
		Node node3 = new Node(3, "e");
		Node node4 = new Node(4, "f");
		
		SingleLinkListManage manage = new SingleLinkListManage();
		manage.addNode(node1);
		manage.addNode(node2);
		manage.addNode(node3);
		manage.addNode(node4);
		System.out.println(getLength(manage.headNode));
		System.out.println(getNode(3, manage));
	}
	
	public static int getLength(Node node) {
		if(node.next == null) {
			return 0;
		}
		int length = 0;
		while(node.next != null) {
			length++;
			node = node.next;
		}
		return length;
	}
	
	public static int getNode(int k, SingleLinkListManage manage) {
		int n = getLength(manage.headNode);
		int i = n - k;
		Node temp = manage.headNode.next;
		if(i > 0) {
			while(true) {
				if(i > 0) {
					temp = temp.next;
					i--;
				}
				return temp.id;
			}
		}
		return -1;
	}
}

双向链表

code

package com.lemon.doublelinkedlist;

public class DoubleLinkList {
	private Node headNode = new Node(0);
	
	//添加数据
	public void add(int value) {
		Node temp1 = headNode;
		Node temp2 = headNode;
		
		while(temp1.next != null) {
			temp2 = temp1;
			temp1 = temp1.next;
		}
		
		temp1.next = new Node(value);
		temp1.pre = temp2;	
	}
	
	//删除数据
	public void delete(int index) {
		Node temp = headNode;
		if(isEmpty()) {
			return;
		}
		for(int i = 0; i < index; i++) {
			temp = temp.next;
		}
		temp.pre.next = temp.next;
		temp.next.pre = temp.pre;
	}
	
	//修改数据
	public void revise(int index, int value) {
		Node temp = headNode;
		if(isEmpty()) {
			return;
		}
		for(int i = 0; i < index; i++) {
			temp = temp.next;
		}
		temp.val = value;
	}
	
	
	//判断数据是否为空
	public boolean isEmpty() {
		if(headNode.pre == headNode.next) {
			return true;
		}
		return false;
	}
	
	//打印
	public void print() {
		Node temp = headNode.next;
		while(temp != null) {
			System.out.println(temp.toString());
			temp = temp.next;
		}
	}
}

class Node {
	public int val;
	public Node pre;
	public Node next;
	
	public Node(int val) {
		this.val = val;
	}

	@Override
	public String toString() {
		return "Node [val=" + val +"]";
	}	
}