2023-06-26 23:08:55 +08:00
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/**
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* File: hash_map_chaining.cs
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* Created Time: 2023-06-26
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* Author: hpstory (hpstory1024@163.com)
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*/
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namespace hello_algo.chapter_hashing;
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/* 链式地址哈希表 */
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class HashMapChaining {
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int size; // 键值对数量
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int capacity; // 哈希表容量
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2023-11-26 23:18:44 +08:00
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double loadThres; // 触发扩容的负载因子阈值
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int extendRatio; // 扩容倍数
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2023-06-26 23:08:55 +08:00
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List<List<Pair>> buckets; // 桶数组
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/* 构造方法 */
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public HashMapChaining() {
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size = 0;
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capacity = 4;
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2023-09-24 20:38:21 +08:00
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loadThres = 2.0 / 3.0;
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2023-06-26 23:08:55 +08:00
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extendRatio = 2;
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buckets = new List<List<Pair>>(capacity);
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for (int i = 0; i < capacity; i++) {
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buckets.Add([]);
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2023-06-26 23:08:55 +08:00
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}
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}
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/* 哈希函数 */
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int HashFunc(int key) {
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return key % capacity;
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}
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/* 负载因子 */
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double LoadFactor() {
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return (double)size / capacity;
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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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// 遍历桶,若找到 key 则返回对应 val
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foreach (Pair pair in buckets[index]) {
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if (pair.key == key) {
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return pair.val;
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}
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}
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// 若未找到 key 则返回 null
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return null;
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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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// 当负载因子超过阈值时,执行扩容
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if (LoadFactor() > loadThres) {
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Extend();
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}
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int index = HashFunc(key);
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// 遍历桶,若遇到指定 key ,则更新对应 val 并返回
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foreach (Pair pair in buckets[index]) {
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if (pair.key == key) {
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pair.val = val;
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return;
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}
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}
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// 若无该 key ,则将键值对添加至尾部
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buckets[index].Add(new Pair(key, val));
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size++;
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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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// 遍历桶,从中删除键值对
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foreach (Pair pair in buckets[index].ToList()) {
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if (pair.key == key) {
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buckets[index].Remove(pair);
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2023-08-01 17:05:40 +08:00
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size--;
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break;
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}
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}
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}
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/* 扩容哈希表 */
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void Extend() {
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// 暂存原哈希表
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List<List<Pair>> bucketsTmp = buckets;
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// 初始化扩容后的新哈希表
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capacity *= extendRatio;
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buckets = new List<List<Pair>>(capacity);
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for (int i = 0; i < capacity; i++) {
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2023-11-26 23:18:44 +08:00
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buckets.Add([]);
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}
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size = 0;
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// 将键值对从原哈希表搬运至新哈希表
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foreach (List<Pair> bucket in bucketsTmp) {
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foreach (Pair pair in bucket) {
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Put(pair.key, pair.val);
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}
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}
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}
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/* 打印哈希表 */
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public void Print() {
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foreach (List<Pair> bucket in buckets) {
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List<string> res = [];
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foreach (Pair pair in bucket) {
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res.Add(pair.key + " -> " + pair.val);
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}
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foreach (string kv in res) {
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Console.WriteLine(kv);
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}
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}
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}
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}
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public class hash_map_chaining {
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[Test]
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public void Test() {
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/* 初始化哈希表 */
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HashMapChaining map = new();
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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(12836, "小哈");
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map.Put(15937, "小啰");
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map.Put(16750, "小算");
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map.Put(13276, "小法");
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map.Put(10583, "小鸭");
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Console.WriteLine("\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(13276);
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Console.WriteLine("\n输入学号 13276 ,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(12836);
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Console.WriteLine("\n删除 12836 后,哈希表为\nKey -> Value");
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map.Print();
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}
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}
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