散列表(拉链法与线性探测法)Java实现

package practice;

import java.security.Principal;
import java.util.Scanner;

import edu.princeton.cs.algs4.*;

public class TestMain {
    public static void main(String[] args) {
        //50个随机数字
        Integer[] a = new Integer[50];
        for (int i = 0; i < a.length; i++) {
            a[i] = new Integer(StdRandom.uniform(1, 1000));
        }

        //50个随机字符串
        char ch = 'a';
        int chl;
        String []b = new String[50];
        for (int i = 0; i < b.length; i++) {
            int sl = StdRandom.uniform(1, 10);
            b[i] = new String();
            for (int j = 0; j < sl; j++) {
                chl = StdRandom.uniform(0, 23);
                b[i] += (char)(ch + chl);
            }
        }
        //构建散列表
        /*SeparateChainingHashST<String, Integer> hashmap = new SeparateChainingHashST<String, Integer>(50);

        for (int i = 0; i < b.length; i++) {
            hashmap.put(b[i], a[i]);
        }*/

        LinearProbingHashST<String, Integer> hashmap = new LinearProbingHashST<String, Integer>();
        //占有率最好在1/2和1/8之间（数学证明结果），占有率越高，查找操作越难以命中，如果占有率为1，输入没有的值就会无限循环
        for (int i = 0; i < b.length; i++) {
            hashmap.put(b[i], a[i]);
        }

        hashmap.show();

        String KeyShuRu;
        Scanner ShuRu = new Scanner(System.in);
        while (true) {
            KeyShuRu = ShuRu.nextLine();
            System.out.println(hashmap.get(KeyShuRu));
            hashmap.delete(KeyShuRu);
            hashmap.show();
        }
    }
}

/*
 * 基于拉链法的散列表
 * 散列值相同时，用一个链表储存
 */
class SeparateChainingHashST<K, V> {
     private K key;
     private V value;
     private int M;
     private SequentialSearchST<K, V>[] st;
     public SeparateChainingHashST(int M) {
         st = (SequentialSearchST<K, V>[]) new SequentialSearchST[M];
         for (int i = 0; i < M; i++) {
            st[i] = new SequentialSearchST();
        }
     }
     /*
      * 插入
      */
     public void put(K key, V value) {
        st[hash(key)].put(key, value);
    }
     /*
      * 查找
      */
     public V get(K key) {
        return st[hash(key)].get(key);
    }
     /*
      * 输出整个表
      */
     public void show() {
        for (int i = 0; i < M; i++) {
            System.out.print("chain ["+i+"]  ");
            st[i].show();
            System.out.println();
        }
    }
     /*
      * 获取哈希值
      */
     private int hash(K key) {
        return (key.hashCode() & 0x7fffffff) % M; //可以返回一个M以内的正整数hash值

    }
}

/*
 * 基于线性探测法的散列表
 * 散列值处已经有元素，就把值存在散列值处的后面（触底返0）
 */
class LinearProbingHashST<K, V> {
     private K[] key;
     private V[] value;
     private int M = 16; //线性探测表的大小
     private int N; //表中键值对的多少
     public LinearProbingHashST() {
         key = (K[]) new Object[M];
         value = (V[]) new Object[M];
    }
     /*
      * 插入
      */
     public void put(K key, V value) {
         if (N >= M/2) { resize(2*M);}

         int hashv = hash(key);
         while (true) {
             if (hashv == M) { hashv = 0;}

             if (this.key[hashv] == null) {
                 this.key[hashv] = key;
                 this.value[hashv] = value;
                 N++;
                 break;
             }
             else if (key.equals(this.key[hashv])) {
                 this.value[hashv] = value;
                 break;
             }

             hashv++;
        }
    }
     /*
      * 查找
      */
     public V get(K key) {
         int hashv = hash(key);
         while (true) {
             System.out.println("hashv = "+hashv);
             if (this.key[hashv] == null) { return null;}
             if (key.equals(this.key[hashv])) { return this.value[hashv];}
             hashv++;
             if (hashv == M) { hashv = 0;}
         }
    }
     /*
      * 输出表
      */
     public void show() {
        for (int i = 0; i < M; i++) {
            System.out.printf("[%d]  %-10s%4d  \n", i, key[i], value[i]);
        }
    }
     /*
      * 删除元素
      */
     public void delete(K key) {
         //将元素删除
         int hashv = hash(key);
         while (true) {
             if (this.key[hashv] == null) {
                 System.out.println("the value is not exist");
                 return;
            }

             if (key.equals(this.key[hashv])) {
                 this.key[hashv]   = null;
                 this.value[hashv] = null;
                 N--;
                 System.out.println("The value has been deleted");
                 break;
            }

             hashv++;
             if (hashv == M) { hashv = 0;}
         }

         //将后面的元素全部重新插入
         hashv = hash(key) + 1;
         while (this.key[hashv] != null) {
             K tempkey   = this.key[hashv];
             V tempvalue = this.value[hashv];

             this.key[hashv]   = null;
             this.value[hashv] = null;
             N--;

             put(tempkey, tempvalue);

             hashv ++;
             if (hashv == M) { hashv = 0;}
        }
    }
     /*
      * 获取哈希值
      */
     private int hash(K key) {
         return (key.hashCode() & 0x7fffffff) % M;
     }
     /*
      * 改变大小
      */
     private void resize(int M) {
        this.M = M;
        K[] tempkey   = (K[]) new Object[M];
        V[] tempvalue = (V[]) new Object[M];

        for (int i = 0; i < key.length; i++) {
            tempkey[i]   = key[i];
            tempvalue[i] = value[i];
        }

        key   = tempkey;
        value = tempvalue;
    }
}

/*
 * 链表
 */
class SequentialSearchST<K, V> {
    private Node head;
    private Node root;
    class Node {
        private K key;
        private V value;
        private Node next;
        private Node(K key, V value) {
            this.key   = key;
            this.value = value;
        }
        /*
         * 输出节点
         */
        private void show() {
            System.out.printf("%-10s%4d  ", key, value);
        }
    }
    /*
     * 插入
     */
    public void put(K key, V value) {
        if (root != null) {
            Node tempnode = root;
            while (true) {
                if (key.equals(tempnode.key)) {
                    tempnode.value = value;
                    return;
                }

                if (tempnode == head) { break;}
                tempnode = tempnode.next;
            }
        }
        //上面是避免有重复的key
        Node newnode = new Node(key, value);
        if (root == null) {
            root = newnode;
            head = newnode;
            return;
        }

        head.next = newnode;
        head = newnode;
    }
    /*
     * 查找
     */
    public V get(K key) {
        Node tempnode = root;

        while (!(tempnode == null)) {
            if (key.equals(tempnode.key)) { return tempnode.value;}
            tempnode = tempnode.next;
        }

        return null;
    }
    /*
     * 输出整条链
     */
    public void show() {
        Node tempnode = root;
        while (!(tempnode == null)) {
            tempnode.show();
            tempnode = tempnode.next;
        }
    }

}