mirror of
https://github.com/krahets/hello-algo.git
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feat(csharp/hashing): add code and update docs to chapter hashing (#568)
* feat(csharp/hashing): add code and update docs to chapter hashing * revert linked list to list
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hpstory
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36
codes/csharp/chapter_hashing/built_in_hash.cs
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36
codes/csharp/chapter_hashing/built_in_hash.cs
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/**
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* File: built_in_hash.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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public class built_in_hash {
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[Test]
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public void Test() {
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int num = 3;
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int hashNum = num.GetHashCode();
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Console.WriteLine("整数 " + num + " 的哈希值为 " + hashNum);
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bool bol = true;
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int hashBol = bol.GetHashCode();
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Console.WriteLine("布尔量 " + bol + " 的哈希值为 " + hashBol);
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double dec = 3.14159;
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int hashDec = dec.GetHashCode();
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Console.WriteLine("小数 " + dec + " 的哈希值为 " + hashDec);
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string str = "Hello 算法";
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int hashStr = str.GetHashCode();
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Console.WriteLine("字符串 " + str + " 的哈希值为 " + hashStr);
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object[] arr = { 12836, "小哈" };
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int hashTup = arr.GetHashCode();
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Console.WriteLine("数组 [" + string.Join(", ", arr) + "] 的哈希值为 " + hashTup);
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ListNode obj = new ListNode(0);
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int hashObj = obj.GetHashCode();
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Console.WriteLine("节点对象 " + obj + " 的哈希值为 " + hashObj);
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}
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}
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143
codes/csharp/chapter_hashing/hash_map_chaining.cs
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143
codes/csharp/chapter_hashing/hash_map_chaining.cs
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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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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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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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loadThres = 2 / 3.0;
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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(new List<Pair>());
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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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return key % capacity;
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}
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/* 负载因子 */
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private 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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}
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}
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size--;
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}
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/* 扩容哈希表 */
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private 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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buckets.Add(new List<Pair>());
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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 = new List<string>();
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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 HashMapChaining();
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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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155
codes/csharp/chapter_hashing/hash_map_open_addressing.cs
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155
codes/csharp/chapter_hashing/hash_map_open_addressing.cs
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/**
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* File: hash_map_open_addressing.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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/* 开放寻址哈希表 */
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class HashMapOpenAddressing {
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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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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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Pair[] buckets; // 桶数组
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Pair removed; // 删除标记
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/* 构造方法 */
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public HashMapOpenAddressing() {
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size = 0;
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capacity = 4;
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loadThres = 2.0 / 3.0;
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extendRatio = 2;
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buckets = new Pair[capacity];
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removed = new Pair(-1, "-1");
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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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return key % capacity;
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}
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/* 负载因子 */
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private 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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// 线性探测，从 index 开始向后遍历
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for (int i = 0; i < capacity; i++) {
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// 计算桶索引，越过尾部返回头部
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int j = (index + i) % capacity;
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// 若遇到空桶，说明无此 key ，则返回 null
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if (buckets[j] == null)
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return null;
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// 若遇到指定 key ，则返回对应 val
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if (buckets[j].key == key && buckets[j] != removed)
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return buckets[j].val;
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}
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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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// 线性探测，从 index 开始向后遍历
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for (int i = 0; i < capacity; i++) {
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// 计算桶索引，越过尾部返回头部
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int j = (index + i) % capacity;
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// 若遇到空桶、或带有删除标记的桶，则将键值对放入该桶
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if (buckets[j] == null || buckets[j] == removed) {
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buckets[j] = new Pair(key, val);
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size += 1;
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return;
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}
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// 若遇到指定 key ，则更新对应 val
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if (buckets[j].key == key) {
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buckets[j].val = val;
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return;
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}
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}
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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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// 线性探测，从 index 开始向后遍历
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for (int i = 0; i < capacity; i++) {
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// 计算桶索引，越过尾部返回头部
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int j = (index + i) % capacity;
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// 若遇到空桶，说明无此 key ，则直接返回
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if (buckets[j] == null) {
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return;
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}
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// 若遇到指定 key ，则标记删除并返回
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if (buckets[j].key == key) {
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buckets[j] = removed;
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size -= 1;
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return;
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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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private void extend() {
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// 暂存原哈希表
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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 Pair[capacity];
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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 (Pair pair in bucketsTmp) {
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if (pair != null && pair != removed) {
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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 (Pair pair in buckets) {
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if (pair != null) {
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Console.WriteLine(pair.key + " -> " + pair.val);
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} else {
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Console.WriteLine("null");
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}
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}
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}
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}
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public class hash_map_open_addressing {
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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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HashMapOpenAddressing map = new HashMapOpenAddressing();
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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(16750);
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Console.WriteLine("\n删除 16750 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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66
codes/csharp/chapter_hashing/simple_hash.cs
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66
codes/csharp/chapter_hashing/simple_hash.cs
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/**
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* File: simple_hash.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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public class simple_hash {
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/* 加法哈希 */
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public static int addHash(string key) {
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long hash = 0;
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const int MODULUS = 1000000007;
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foreach (char c in key) {
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hash = (hash + c) % MODULUS;
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}
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return (int)hash;
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}
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/* 乘法哈希 */
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public static int mulHash(string key) {
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long hash = 0;
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const int MODULUS = 1000000007;
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foreach (char c in key) {
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hash = (31 * hash + c) % MODULUS;
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}
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return (int)hash;
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}
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/* 异或哈希 */
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public static int xorHash(string key) {
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int hash = 0;
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const int MODULUS = 1000000007;
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foreach (char c in key) {
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hash ^= c;
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}
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return hash & MODULUS;
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}
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/* 旋转哈希 */
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public static int rotHash(string key) {
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long hash = 0;
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const int MODULUS = 1000000007;
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foreach (char c in key) {
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hash = ((hash << 4) ^ (hash >> 28) ^ c) % MODULUS;
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}
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return (int)hash;
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}
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[Test]
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public void Test() {
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string key = "Hello 算法";
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int hash = addHash(key);
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Console.WriteLine("加法哈希值为 " + hash);
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hash = mulHash(key);
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Console.WriteLine("乘法哈希值为 " + hash);
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hash = xorHash(key);
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Console.WriteLine("异或哈希值为 " + hash);
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hash = rotHash(key);
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Console.WriteLine("旋转哈希值为 " + hash);
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}
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}
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@ -338,7 +338,29 @@ $$
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=== "C#"
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```csharp title="built_in_hash.cs"
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int num = 3;
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int hashNum = num.GetHashCode();
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// 整数 3 的哈希值为 3;
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bool bol = true;
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int hashBol = bol.GetHashCode();
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// 布尔量 true 的哈希值为 1;
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double dec = 3.14159;
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int hashDec = dec.GetHashCode();
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// 小数 3.14159 的哈希值为 -1340954729;
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string str = "Hello 算法";
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int hashStr = str.GetHashCode();
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// 字符串 Hello 算法 的哈希值为 -586107568;
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object[] arr = { 12836, "小哈" };
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int hashTup = arr.GetHashCode();
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// 数组 [12836, 小哈] 的哈希值为 42931033;
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ListNode obj = new ListNode(0);
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int hashObj = obj.GetHashCode();
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// 节点对象 0 的哈希值为 39053774;
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```
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=== "Swift"
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