139 lines
3.6 KiB
Java
139 lines
3.6 KiB
Java
/*
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* File: hash_map.java
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* Created Time: 2022-12-04
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* Author: Krahets (krahets@163.com)
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*/
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package chapter_hashing;
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import java.util.*;
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/* 键值对 int->String */
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class Entry {
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public int key;
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public String val;
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public Entry(int key, String val) {
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this.key = key;
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this.val = val;
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}
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}
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/* 基于数组简易实现的哈希表 */
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class ArrayHashMap {
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private List<Entry> bucket;
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public ArrayHashMap() {
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// 初始化一个长度为 10 的桶（数组）
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bucket = new ArrayList<>(10);
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for (int i = 0; i < 10; i++) {
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bucket.add(null);
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}
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}
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/* 哈希函数 */
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private int hashFunc(int key) {
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int index = key % 10000;
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return index;
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}
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/* 查询操作 */
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public String get(int key) {
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int index = hashFunc(key);
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Entry pair = bucket.get(index);
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if (pair == null) return null;
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return pair.val;
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}
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/* 添加操作 */
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public void put(int key, String val) {
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Entry pair = new Entry(key, val);
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int index = hashFunc(key);
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bucket.set(index, pair);
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}
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/* 删除操作 */
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public void remove(int key) {
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int index = hashFunc(key);
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// 置为空字符，代表删除
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bucket.set(index, null);
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}
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/* 获取所有键值对 */
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public List<Entry> entrySet() {
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List<Entry> entrySet = new ArrayList<>();
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for (Entry pair : bucket) {
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if (pair != null)
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entrySet.add(pair);
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}
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return entrySet;
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}
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/* 获取所有键 */
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public List<Integer> keySet() {
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List<Integer> keySet = new ArrayList<>();
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for (Entry pair : bucket) {
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if (pair != null)
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keySet.add(pair.key);
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}
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return keySet;
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}
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/* 获取所有值 */
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public List<String> valueSet() {
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List<String> valueSet = new ArrayList<>();
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for (Entry pair : bucket) {
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if (pair != null)
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valueSet.add(pair.val);
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}
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return valueSet;
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}
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/* 打印哈希表 */
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public void print() {
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for (Entry kv: entrySet()) {
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System.out.println(kv.key + " -> " + kv.val);
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}
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}
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}
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public class array_hash_map {
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public static void main(String[] args) {
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/* 初始化哈希表 */
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ArrayHashMap map = new ArrayHashMap();
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/* 添加操作 */
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// 在哈希表中添加键值对 (key, value)
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map.put(10001, "小哈");
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map.put(10002, "小啰");
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map.put(10003, "小算");
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map.put(10004, "小法");
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map.put(10005, "小哇");
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System.out.println("\n添加完成后，哈希表为\nKey -> Value");
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map.print();
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/* 查询操作 */
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// 向哈希表输入键 key ，得到值 value
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String name = map.get(10002);
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System.out.println("\n输入学号 10002 ，查询到姓名 " + name);
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/* 删除操作 */
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// 在哈希表中删除键值对 (key, value)
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map.remove(10005);
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System.out.println("\n删除 10005 后，哈希表为\nKey -> Value");
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map.print();
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/* 遍历哈希表 */
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System.out.println("\n遍历键值对 Key->Value");
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for (Entry kv: map.entrySet()) {
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System.out.println(kv.key + " -> " + kv.val);
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}
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System.out.println("\n单独遍历键 Key");
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for (int key: map.keySet()) {
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System.out.println(key);
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}
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System.out.println("\n单独遍历值 Value");
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for (String val: map.valueSet()) {
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System.out.println(val);
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}
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}
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}
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