HMJAVA数据结构与算法5【符号表】

1、符号表API设计

 

 

 

 

 

 

2、符号表实现

package cn.itcast.algorithm.symbol;

public class SymbolTable<Key,Value> {
    //记录首结点
    private Node head;
    //记录符号表中元素的个数
    private int N;

    private class Node{
        //键
        public Key key;
        //值
        public Value value;
        //下一个结点
        public Node next;

        public Node(Key key, Value value, Node next) {
            this.key = key;
            this.value = value;
            this.next = next;
        }
    }

    public SymbolTable() {
        this.head = new Node(null,null,null);
        this.N=0;
    }

    //获取符号表中键值对的个数
    public int size(){
        return N;
    }

    //往符号表中插入键值对
    public void put(Key key,Value value){
        //符号表中已经存在了键为key的键值对，那么只需要找到该结点，替换值为value即可
        Node n = head;
        while(n.next!=null){
            //变换n
            n = n.next;
            //判断n结点存储的键是否为key，如果是，则替换n结点的值
            if (n.key.equals(key)){
                n.value = value;
                return;
            }

        }

        //如果符号表中不存在键为key的键值对，只需要创建新的结点，保存要插入的键值对，把新结点插入到链表的头部  head.next=新结点即可
        Node newNode = new Node(key, value, null);
        Node oldFirst = head.next;
        newNode.next = oldFirst;
        head.next = newNode;


        //元素个数+1；
        N++;

    }
    //删除符号表中键为key的键值对
    public void delete(Key key){
        //找到键为key的结点，把该结点从链表中删除

        Node n = head;
        while(n.next!=null){
            //判断n结点的下一个结点的键是否为key，如果是，就删除该结点
            if (n.next.key.equals(key)){
                n.next = n.next.next;
                N--;
                return;
            }


            //变换n
            n = n.next;
        }
    }

    //从符号表中获取key对应的值
    public Value get(Key key){
        //找到键为key的结点
        Node n = head;
        while(n.next!=null){
            //变换n
            n = n.next;
            if (n.key.equals(key)){
                return n.value;
            }
        }
        return null;
    }


}

View Code

 

package cn.itcast.algorithm.test;

import cn.itcast.algorithm.symbol.SymbolTable;

public class SymbolTableTest {
    public static void main(String[] args) {
        //创建符号表对象
        SymbolTable<Integer, String> symbolTable = new SymbolTable<>();

        //测试put方法（插入,替换）
        symbolTable.put(1,"乔峰");
        symbolTable.put(2,"虚竹");
        symbolTable.put(3,"段誉");

        System.out.println("插入完毕后，元素的个数为:"+symbolTable.size());

        symbolTable.put(2, "慕容复");
        System.out.println("替换完毕后的元素的个数为:"+symbolTable.size());

        //测试get方法
        System.out.println("替换完毕后，键2对应的值为:"+symbolTable.get(2));

        //测试删除方法
        symbolTable.delete(2);
        System.out.println("删除完毕后，元素的个数:"+symbolTable.size());


    }
}

View Code

 

3、有序符号表

 

 

package cn.itcast.algorithm.symbol;

public class OrderSymbolTable<Key extends Comparable<Key>,Value> {
    //记录首结点
    private Node head;
    //记录符号表中元素的个数
    private int N;

    private class Node{
        //键
        public Key key;
        //值
        public Value value;
        //下一个结点
        public Node next;

        public Node(Key key, Value value, Node next) {
            this.key = key;
            this.value = value;
            this.next = next;
        }
    }

    public OrderSymbolTable() {
        this.head = new Node(null,null,null);
        this.N=0;
    }

    //获取符号表中键值对的个数
    public int size(){
        return N;
    }

    //往符号表中插入键值对
    public void put(Key key,Value value){
        //定义两个Node变量，分别记录当前结点和当前结点的上一个结点

        Node curr = head.next;
        Node pre = head;
        while(curr!=null && key.compareTo(curr.key)>0){

            //变换当前结点和前一个结点即可
            pre = curr;
            curr = curr.next;
        }

        //如果当前结点curr的键和要插入的key一样，则替换
        if (curr!=null && key.compareTo(curr.key)==0){
            curr.value = value;
            return;
        }

        //如果当前结点curr的键和要插入的key不一样，把新的结点插入到curr之前
        Node newNode = new Node(key, value, curr);
        pre.next = newNode;

        //元素的个数+1；
        N++;

    }
    //删除符号表中键为key的键值对
    public void delete(Key key){
        //找到键为key的结点，把该结点从链表中删除

        Node n = head;
        while(n.next!=null){
            //判断n结点的下一个结点的键是否为key，如果是，就删除该结点
            if (n.next.key.equals(key)){
                n.next = n.next.next;
                N--;
                return;
            }


            //变换n
            n = n.next;
        }
    }

    //从符号表中获取key对应的值
    public Value get(Key key){
        //找到键为key的结点
        Node n = head;
        while(n.next!=null){
            //变换n
            n = n.next;
            if (n.key.equals(key)){
                return n.value;
            }
        }
        return null;
    }


}

View Code

package cn.itcast.algorithm.test;

import cn.itcast.algorithm.symbol.OrderSymbolTable;

public class OrderSymbolTableTest {

    public static void main(String[] args) {
        //创建有序符号表对象
        OrderSymbolTable<Integer, String> table = new OrderSymbolTable<>();

        table.put(1,"张三");
        table.put(2,"李四");
        table.put(4,"赵六");
        table.put(7,"田七");

        table.put(3,"王五");

    }
}

View Code