有序平行数组实现符号表

有序平行数组实现符号表

2019-06-27  17:35:23

import java.io.ObjectInputStream;
import java.util.ArrayList;
import java.util.Arrays;

/**
 * @ClassName ArrayST
 * @Author wangyudi
 * @Date 2019/6/27 16:46
 * @Version 1.0
 * @Description 有序平行数组实现符号表
 * 成员变量：键数组、值数组、数量
 * 成员函数：获取值get()、添加/更新值put()、获取键的排名rank()、删除键值对delete()、获取大小size()、显示display()、调整内部数组的大小
 *
 */
public class ArrayST<Key extends Comparable<Key>, Value> {
    private Key[] keys;
    private Value[] values;
    private int count;

    public ArrayST() {
        this.count = 0;
        keys = (Key[])new Comparable[3];
        values = (Value[])new Object[3];
    }

    private void resize(int num){
        Key[] tempKeys = (Key[])new Comparable[num];
        Value[] tempValues = (Value[])new Object[num];
        for(int i=0;i<count;i++){
            tempKeys[i]=keys[i];
            tempValues[i]=values[i];
        }
        keys = tempKeys;
        values = tempValues;
    }

    public int size(){
        return count;
    }

    public void display(){
        for(int i=0;i<count;i++){
            System.out.print(keys[i]+"    ");
        }
        System.out.println();
        for(int i=0;i<count;i++){
            System.out.print(values[i]+"  ");
        }
        System.out.println();
    }

    public Value get(Key key){
        int j = rank(key,0,count-1);
        if(j < count && keys[j].compareTo(key)==0){
            return values[j];
        }
        return null;
    }

    public void put(Key key, Value value){
        int j = rank(key,0,count-1);
        if(j < count && keys[j]==key){
            values[j]=value;
            return;
        }

        if(count>=keys.length) resize(keys.length*2);
        for(int i=count-1;i>=j;i--){
            keys[i+1]=keys[i];
            values[i+1]=values[i];
        }
        keys[j] = key;
        values[j] = value;
        count++;
    }

    public void delete(Key key){
        int j = rank(key,0,count-1);
        if(j<count&&keys[j].compareTo(key)==0){  //use compareTo() to compare two keys
            for(;j<count-1;j++){
                keys[j] = keys[j+1];
                values[j]=values[j+1];
            }
            count--;
        }
    }

    /**
     * rank方法是有序平行数组实现符号表的关键
     * @param key
     * @return 该键的排名，即比多少个键大
     */
    public int rank(Key key, int lo, int hi){
        if(lo>hi) return lo;
        int mid = lo+(hi-lo)/2;
        int cmp = keys[mid].compareTo(key);
        if(cmp<0){
            return rank(key,mid+1,hi);
        }else if(cmp>0){
            return rank(key,lo,mid-1);
        }else{
            return mid;
        }
    }
}

/**
 * @ClassName TestCase
 * @Author wangyudi
 * @Date 2019/6/27 17:23
 * @Version 1.0
 * @Description  测试案例
 */
public class TestCase {
    public static void main(String[] args) {
        ArrayST<Integer, String> st = new ArrayST<>();
        st.put(5,"5..");
        st.put(2,"2..");
        st.put(34,"34..");
        st.put(17,"17..");
        st.put(55,"55..");
        st.put(214,"214..");
        st.delete(34);

        System.out.println(st.get(214));
        System.out.println(st.size());

        st.display();
    }
}


//结果
214..
5
2    5    17    55    214    
2..  5..  17..  55..  214..