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Add Java and C++ code for the section hash algorithm (#560)
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6 changed files with 256 additions and 11 deletions
29
codes/cpp/chapter_hashing/built_in_hash.cpp
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29
codes/cpp/chapter_hashing/built_in_hash.cpp
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/**
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* File: built_in_hash.cpp
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* Created Time: 2023-06-21
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* Author: Krahets (krahets@163.com)
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*/
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#include "../utils/common.hpp"
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/* Driver Code */
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int main() {
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int num = 3;
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size_t hashNum = hash<int>()(num);
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cout << "整数 " << num << " 的哈希值为 " << hashNum << "\n";
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bool bol = true;
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size_t hashBol = hash<bool>()(bol);
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cout << "布尔量 " << bol << " 的哈希值为 " << hashBol << "\n";
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double dec = 3.14159;
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size_t hashDec = hash<double>()(dec);
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cout << "小数 " << dec << " 的哈希值为 " << hashDec << "\n";
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string str = "Hello 算法";
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size_t hashStr = hash<string>()(str);
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cout << "字符串 " << str << " 的哈希值为 " << hashStr << "\n";
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// 在 C++ 中,内置 std:hash() 仅提供基本数据类型的哈希值计算
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// 数组、对象的哈希值计算需要自行实现
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}
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67
codes/cpp/chapter_hashing/simple_hash.cpp
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67
codes/cpp/chapter_hashing/simple_hash.cpp
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/**
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* File: simple_hash.cpp
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* Created Time: 2023-06-21
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* Author: Krahets (krahets@163.com)
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*/
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#include "../utils/common.hpp"
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/* 加法哈希 */
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int addHash(string key) {
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long long hash = 0;
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const int MODULUS = 1000000007;
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for (unsigned char c : key) {
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hash = (hash + (int)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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int mulHash(string key) {
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long long hash = 0;
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const int MODULUS = 1000000007;
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for (unsigned char c : key) {
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hash = (31 * hash + (int)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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int xorHash(string key) {
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int hash = 0;
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const int MODULUS = 1000000007;
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for (unsigned char c : key) {
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cout<<(int)c<<endl;
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hash ^= (int)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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int rotHash(string key) {
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long long hash = 0;
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const int MODULUS = 1000000007;
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for (unsigned char c : key) {
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hash = ((hash << 4) ^ (hash >> 28) ^ (int)c) % MODULUS;
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}
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return (int)hash;
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}
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/* Driver Code */
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int main() {
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string key = "Hello dsad3241241dsa算123法";
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int hash = addHash(key);
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cout << "加法哈希值为 " << hash << endl;
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hash = mulHash(key);
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cout << "乘法哈希值为 " << hash << endl;
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hash = xorHash(key);
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cout << "异或哈希值为 " << hash << endl;
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hash = rotHash(key);
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cout << "旋转哈希值为 " << hash << endl;
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return 0;
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}
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38
codes/java/chapter_hashing/built_in_hash.java
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38
codes/java/chapter_hashing/built_in_hash.java
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/**
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* File: built_in_hash.java
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* Created Time: 2023-06-21
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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 utils.*;
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import java.util.*;
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public class built_in_hash {
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public static void main(String[] args) {
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int num = 3;
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int hashNum = Integer.hashCode(num);
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System.out.println("整数 " + num + " 的哈希值为 " + hashNum);
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boolean bol = true;
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int hashBol = Boolean.hashCode(bol);
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System.out.println("布尔量 " + bol + " 的哈希值为 " + hashBol);
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double dec = 3.14159;
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int hashDec = Double.hashCode(dec);
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System.out.println("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.hashCode();
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System.out.println("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 = Arrays.hashCode(arr);
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System.out.println("数组 " + Arrays.toString(arr) + " 的哈希值为 " + hashTup);
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ListNode obj = new ListNode(0);
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int hashObj = obj.hashCode();
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System.out.println("节点对象 " + obj + " 的哈希值为 " + hashObj);
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}
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}
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66
codes/java/chapter_hashing/simple_hash.java
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66
codes/java/chapter_hashing/simple_hash.java
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/**
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* File: simple_hash.java
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* Created Time: 2023-06-21
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* Author: Krahets (krahets@163.com)
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*/
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package chapter_hashing;
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public class simple_hash {
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/* 加法哈希 */
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static int addHash(String key) {
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long hash = 0;
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final int MODULUS = 1000000007;
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for (char c : key.toCharArray()) {
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hash = (hash + (int) 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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static int mulHash(String key) {
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long hash = 0;
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final int MODULUS = 1000000007;
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for (char c : key.toCharArray()) {
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hash = (31 * hash + (int) 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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static int xorHash(String key) {
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int hash = 0;
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final int MODULUS = 1000000007;
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for (char c : key.toCharArray()) {
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System.out.println((int)c);
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hash ^= (int) 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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static int rotHash(String key) {
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long hash = 0;
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final int MODULUS = 1000000007;
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for (char c : key.toCharArray()) {
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hash = ((hash << 4) ^ (hash >> 28) ^ (int) c) % MODULUS;
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}
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return (int) hash;
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}
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public static void main(String[] args) {
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String key = "Hello 算法";
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int hash = addHash(key);
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System.out.println("加法哈希值为 " + hash);
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hash = mulHash(key);
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System.out.println("乘法哈希值为 " + hash);
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hash = xorHash(key);
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System.out.println("异或哈希值为 " + hash);
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hash = rotHash(key);
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System.out.println("旋转哈希值为 " + hash);
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}
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}
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@ -43,14 +43,16 @@ def rot_hash(key: str) -> int:
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"""Driver Code"""
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if __name__ == "__main__":
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hash = add_hash("Hello 算法")
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key = "Hello 算法"
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hash = add_hash(key)
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print(f"加法哈希值为 {hash}")
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hash = mul_hash("Hello 算法")
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hash = mul_hash(key)
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print(f"乘法哈希值为 {hash}")
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hash = xor_hash("Hello 算法")
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hash = xor_hash(key)
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print(f"异或哈希值为 {hash}")
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hash = rot_hash("Hello 算法")
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hash = rot_hash(key)
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print(f"旋转哈希值为 {hash}")
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@ -211,13 +211,13 @@ $$
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直至目前,MD5 和 SHA-1 已多次被成功攻击,因此它们被各类安全应用弃用。SHA-2 系列中的 SHA-256 是最安全的哈希算法之一,仍未出现成功的攻击案例,因此常被用在各类安全应用与协议中。SHA-3 相较 SHA-2 的实现开销更低、计算效率更高,但目前使用覆盖度不如 SHA-2 系列。
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| | MD5 | SHA-1 | SHA-2 | SHA-3 |
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| -------- | ------------------------------ | -------------------- | ---------------------------- | -------------------- |
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| 推出时间 | 1992 | 1995 | 2002 | 2008 |
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| 输出长度 | 128 bits | 160 bits | 256 / 512 bits | 224/256/384/512 bits |
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| 哈希冲突 | 较多 | 较多 | 很少 | 很少 |
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| 安全等级 | 低,已被成功攻击 | 低,已被成功攻击 | 高 | 高 |
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| 应用 | 已被弃用,仍用于数据完整性检查 | 已被弃用 | 加密货币交易验证、数字签名等 | 可用于替代 SHA-2 |
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| | MD5 | SHA-1 | SHA-2 | SHA-3 |
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| -------- | ------------------------------ | ---------------- | ---------------------------- | -------------------- |
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| 推出时间 | 1992 | 1995 | 2002 | 2008 |
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| 输出长度 | 128 bits | 160 bits | 256 / 512 bits | 224/256/384/512 bits |
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| 哈希冲突 | 较多 | 较多 | 很少 | 很少 |
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| 安全等级 | 低,已被成功攻击 | 低,已被成功攻击 | 高 | 高 |
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| 应用 | 已被弃用,仍用于数据完整性检查 | 已被弃用 | 加密货币交易验证、数字签名等 | 可用于替代 SHA-2 |
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## 数据结构的哈希值
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- 元组的哈希值是对其中每一个元素进行哈希,然后将这些哈希值组合起来,得到单一的哈希值。
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- 对象的哈希值基于其内存地址生成。通过重写对象的哈希方法,可实现基于内容生成哈希值。
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!!! tip
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请注意,不同编程语言的内置哈希值计算函数的定义和方法不同。
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=== "Java"
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```java title="built_in_hash.java"
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int num = 3;
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int hashNum = Integer.hashCode(num);
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// 整数 3 的哈希值为 3
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boolean bol = true;
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int hashBol = Boolean.hashCode(bol);
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// 布尔量 true 的哈希值为 1231
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double dec = 3.14159;
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int hashDec = Double.hashCode(dec);
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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.hashCode();
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// 字符串 Hello 算法 的哈希值为 -727081396
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Object[] arr = { 12836, "小哈" };
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int hashTup = Arrays.hashCode(arr);
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// 数组 [12836, 小哈] 的哈希值为 1151158
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ListNode obj = new ListNode(0);
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int hashObj = obj.hashCode();
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// 节点对象 utils.ListNode@7dc5e7b4 的哈希值为 2110121908
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```
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=== "C++"
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```cpp title="built_in_hash.cpp"
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int num = 3;
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size_t hashNum = hash<int>()(num);
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// 整数 3 的哈希值为 3
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bool bol = true;
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size_t hashBol = hash<bool>()(bol);
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// 布尔量 1 的哈希值为 1
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double dec = 3.14159;
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size_t hashDec = hash<double>()(dec);
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// 小数 3.14159 的哈希值为 4614256650576692846
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string str = "Hello 算法";
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size_t hashStr = hash<string>()(str);
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// 字符串 Hello 算法 的哈希值为 15466937326284535026
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// 在 C++ 中,内置 std:hash() 仅提供基本数据类型的哈希值计算
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// 数组、对象的哈希值计算需要自行实现
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```
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=== "Python"
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