The symbol table

• 符号表最主要的目的就是将一个键和一个值联系起来,符号表能够将存储的数据元素是一个键和一个值共同组成的键值对数据,我们可以根据键来查找对应的值.
• The keys in the symbol table have 唯一性

Symbol table practical application

符号表API设计

节点类API

符号表API

package symbol;

/** * @ClassName SymbolTable * @Authoc 孙少聪 * @Date 2022/8/3 09:32:37 */

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

    private class Node{
    
        // 键
        private Key key;
        // 值
        private 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;
    }

    public int size(){
    
        return N;
    }

    public void put(Key key,Value value){
    
        // 符号表中已经存在键为key的键值对,那么只需要找到该结点,替换为value的即可
        Node  n = head;
        while (n.next!=null){
    
            n = n.next;
            if(n.key.equals(key)){
    
                n.value = value;
                return;
            }
        }
        // does not exist in the symbol tablekey的键值对,Then you need to create a new tie,保存要插入的键值对,Insert the new node into the head of the two tables.
        Node newNode = new Node(key, value, null);
        Node oldFirst = head.next;
        head.next = newNode;
        newNode.next = oldFirst;
        // 元素个数加1
        N++;
    }

    public void delete(Key key){
    
        Node  n = head;
        while (n.next!=null){
    
            if(n.next.key.equals(key)){
    
                n.next = n.next.next;
                N--;
                return;
            }
            // 变换n
            n = n.next;
        }

    }

    public Value get(Key key){
    
        Node  n = head;
        while (n.next!=null){
    
            // 变换n
            n = n.next;
            if(n.key.equals(key)){
    
                return n.value;
            }
        }
        return null;
    }
}

• 测试

    public static void main(String[] args) {
    
        // 创建符号表对象
        SymbolTable<Integer, String> symbolTable = new SymbolTable<>();
        // 调试put对象s
        symbolTable.put(1,"乔峰");
        symbolTable.put(2,"虚竹");
        symbolTable.put(3,"段誉");
        System.out.println(symbolTable.size());
        symbolTable.put(1,"孙少聪");
        System.out.println(symbolTable.size());

        // get方法
        System.out.println(symbolTable.get(1));

        // delete
        symbolTable.delete(2);
        System.out.println(symbolTable.size());
    }

有序符号表

package symbol;

/** * @ClassName SymbolTable * @Authoc 孙少聪 * @Date 2022/8/3 09:32:37 */

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

    private class Node{
    
        // 键
        private Key key;
        // 值
        private 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;
    }

    public int size(){
    
        return N;
    }

    public void put(Key key,Value value){
    
        // 符号表中已经存在键为key的键值对,那么只需要找到该结点,替换为value的即可
        Node  pre = head;
        Node  curr = head.next;
        while (curr != null && key.compareTo(curr.key)>0){
    
            // Change the current node and the previous node
            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;
        }
        // key不一样,Insert the new node into itcurr之前
        Node newNode = new Node(key, value, null);
        pre.next = newNode;
        newNode.next = curr;
        // 元素个数加1
        N++;
    }

    public void delete(Key key){
    
        Node  n = head;
        while (n.next!=null){
    
            if(n.next.key.equals(key)){
    
                n.next = n.next.next;
                N--;
                return;
            }
            // 变换n
            n = n.next;
        }

    }

    public Value get(Key key){
    
        Node  n = head;
        while (n.next!=null){
    
            // 变换n
            n = n.next;
            if(n.key.equals(key)){
    
                return n.value;
            }
        }
        return null;
    }
}

• 测试（View the data stored in the symbol table by debugging）

   public static void main(String[] args) {
    
        // 创建符号表对象
        OrderSymbolTable<Integer, String> symbolTable = new OrderSymbolTable<>();
        // 调试put对象s
        symbolTable.put(1,"乔峰");
        symbolTable.put(2,"虚竹");
        symbolTable.put(4,"段誉");
        symbolTable.put(3,"孙少聪");

    }