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Add Java and C++ code for the section hash algorithm (#560)

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Yudong Jin 2023-06-21 19:26:16 +08:00 committed by GitHub
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6 changed files with 256 additions and 11 deletions
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29
codes/cpp/chapter_hashing/built_in_hash.cpp Normal file
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/**
* File: built_in_hash.cpp
* Created Time: 2023-06-21
* Author: Krahets (krahets@163.com)
*/
#include "../utils/common.hpp"
/* Driver Code */
int main() {
int num = 3;
size_t hashNum = hash<int>()(num);
cout << "整数 " << num << " 的哈希值为 " << hashNum << "\n";
bool bol = true;
size_t hashBol = hash<bool>()(bol);
cout << "布尔量 " << bol << " 的哈希值为 " << hashBol << "\n";
double dec = 3.14159;
size_t hashDec = hash<double>()(dec);
cout << "小数 " << dec << " 的哈希值为 " << hashDec << "\n";
string str = "Hello 算法";
size_t hashStr = hash<string>()(str);
cout << "字符串 " << str << " 的哈希值为 " << hashStr << "\n";
// 在 C++ 中，内置 std:hash() 仅提供基本数据类型的哈希值计算
// 数组、对象的哈希值计算需要自行实现
}

67
codes/cpp/chapter_hashing/simple_hash.cpp Normal file
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/**
* File: simple_hash.cpp
* Created Time: 2023-06-21
* Author: Krahets (krahets@163.com)
*/
#include "../utils/common.hpp"
/* 加法哈希 */
int addHash(string key) {
long long hash = 0;
const int MODULUS = 1000000007;
for (unsigned char c : key) {
hash = (hash + (int)c) % MODULUS;
}
return (int)hash;
}
/* 乘法哈希 */
int mulHash(string key) {
long long hash = 0;
const int MODULUS = 1000000007;
for (unsigned char c : key) {
hash = (31 * hash + (int)c) % MODULUS;
}
return (int)hash;
}
/* 异或哈希 */
int xorHash(string key) {
int hash = 0;
const int MODULUS = 1000000007;
for (unsigned char c : key) {
cout<<(int)c<<endl;
hash ^= (int)c;
}
return hash & MODULUS;
}
/* 旋转哈希 */
int rotHash(string key) {
long long hash = 0;
const int MODULUS = 1000000007;
for (unsigned char c : key) {
hash = ((hash << 4) ^ (hash >> 28) ^ (int)c) % MODULUS;
}
return (int)hash;
}
/* Driver Code */
int main() {
string key = "Hello dsad3241241dsa算123法";
int hash = addHash(key);
cout << "加法哈希值为 " << hash << endl;
hash = mulHash(key);
cout << "乘法哈希值为 " << hash << endl;
hash = xorHash(key);
cout << "异或哈希值为 " << hash << endl;
hash = rotHash(key);
cout << "旋转哈希值为 " << hash << endl;
return 0;
}

38
codes/java/chapter_hashing/built_in_hash.java Normal file
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/**
* File: built_in_hash.java
* Created Time: 2023-06-21
* Author: Krahets (krahets@163.com)
*/
package chapter_hashing;
import utils.*;
import java.util.*;
public class built_in_hash {
public static void main(String[] args) {
int num = 3;
int hashNum = Integer.hashCode(num);
System.out.println("整数 " + num + " 的哈希值为 " + hashNum);
boolean bol = true;
int hashBol = Boolean.hashCode(bol);
System.out.println("布尔量 " + bol + " 的哈希值为 " + hashBol);
double dec = 3.14159;
int hashDec = Double.hashCode(dec);
System.out.println("小数 " + dec + " 的哈希值为 " + hashDec);
String str = "Hello 算法";
int hashStr = str.hashCode();
System.out.println("字符串 " + str + " 的哈希值为 " + hashStr);
Object[] arr = { 12836, "小哈" };
int hashTup = Arrays.hashCode(arr);
System.out.println("数组 " + Arrays.toString(arr) + " 的哈希值为 " + hashTup);
ListNode obj = new ListNode(0);
int hashObj = obj.hashCode();
System.out.println("节点对象 " + obj + " 的哈希值为 " + hashObj);
}
}

66
codes/java/chapter_hashing/simple_hash.java Normal file
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/**
* File: simple_hash.java
* Created Time: 2023-06-21
* Author: Krahets (krahets@163.com)
*/
package chapter_hashing;
public class simple_hash {
/* 加法哈希 */
static int addHash(String key) {
long hash = 0;
final int MODULUS = 1000000007;
for (char c : key.toCharArray()) {
hash = (hash + (int) c) % MODULUS;
}
return (int) hash;
}
/* 乘法哈希 */
static int mulHash(String key) {
long hash = 0;
final int MODULUS = 1000000007;
for (char c : key.toCharArray()) {
hash = (31 * hash + (int) c) % MODULUS;
}
return (int) hash;
}
/* 异或哈希 */
static int xorHash(String key) {
int hash = 0;
final int MODULUS = 1000000007;
for (char c : key.toCharArray()) {
System.out.println((int)c);
hash ^= (int) c;
}
return hash & MODULUS;
}
/* 旋转哈希 */
static int rotHash(String key) {
long hash = 0;
final int MODULUS = 1000000007;
for (char c : key.toCharArray()) {
hash = ((hash << 4) ^ (hash >> 28) ^ (int) c) % MODULUS;
}
return (int) hash;
}
public static void main(String[] args) {
String key = "Hello 算法";
int hash = addHash(key);
System.out.println("加法哈希值为 " + hash);
hash = mulHash(key);
System.out.println("乘法哈希值为 " + hash);
hash = xorHash(key);
System.out.println("异或哈希值为 " + hash);
hash = rotHash(key);
System.out.println("旋转哈希值为 " + hash);
}
}

10
codes/python/chapter_hashing/simple_hash.py
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@ -43,14 +43,16 @@ def rot_hash(key: str) -> int:
"""Driver Code"""
if __name__ == "__main__":
hash = add_hash("Hello 算法")
key = "Hello 算法"
hash = add_hash(key)
print(f"加法哈希值为 {hash}")
hash = mul_hash("Hello 算法")
hash = mul_hash(key)
print(f"乘法哈希值为 {hash}")
hash = xor_hash("Hello 算法")
hash = xor_hash(key)
print(f"异或哈希值为 {hash}")
hash = rot_hash("Hello 算法")
hash = rot_hash(key)
print(f"旋转哈希值为 {hash}")

45
docs/chapter_hashing/hash_algorithm.md
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@ -212,7 +212,7 @@ $$
直至目前，MD5 和 SHA-1 已多次被成功攻击，因此它们被各类安全应用弃用。SHA-2 系列中的 SHA-256 是最安全的哈希算法之一，仍未出现成功的攻击案例，因此常被用在各类安全应用与协议中。SHA-3 相较 SHA-2 的实现开销更低、计算效率更高，但目前使用覆盖度不如 SHA-2 系列。
| | MD5 | SHA-1 | SHA-2 | SHA-3 |
| -------- | ------------------------------ | -------------------- | ---------------------------- | -------------------- |
| -------- | ------------------------------ | ---------------- | ---------------------------- | -------------------- |
| 推出时间 | 1992 | 1995 | 2002 | 2008 |
| 输出长度 | 128 bits | 160 bits | 256 / 512 bits | 224/256/384/512 bits |
| 哈希冲突 | 较多 | 较多 | 很少 | 很少 |
@ -228,16 +228,59 @@ $$
- 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。
- 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。
!!! tip
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。
=== "Java"
```java title="built_in_hash.java"
int num = 3;
int hashNum = Integer.hashCode(num);
// 整数 3 的哈希值为 3
boolean bol = true;
int hashBol = Boolean.hashCode(bol);
// 布尔量 true 的哈希值为 1231
double dec = 3.14159;
int hashDec = Double.hashCode(dec);
// 小数 3.14159 的哈希值为 -1340954729
String str = "Hello 算法";
int hashStr = str.hashCode();
// 字符串 Hello 算法 的哈希值为 -727081396
Object[] arr = { 12836, "小哈" };
int hashTup = Arrays.hashCode(arr);
// 数组 [12836, 小哈] 的哈希值为 1151158
ListNode obj = new ListNode(0);
int hashObj = obj.hashCode();
// 节点对象 utils.ListNode@7dc5e7b4 的哈希值为 2110121908
```
=== "C++"
```cpp title="built_in_hash.cpp"
int num = 3;
size_t hashNum = hash<int>()(num);
// 整数 3 的哈希值为 3
bool bol = true;
size_t hashBol = hash<bool>()(bol);
// 布尔量 1 的哈希值为 1
double dec = 3.14159;
size_t hashDec = hash<double>()(dec);
// 小数 3.14159 的哈希值为 4614256650576692846
string str = "Hello 算法";
size_t hashStr = hash<string>()(str);
// 字符串 Hello 算法 的哈希值为 15466937326284535026
// 在 C++ 中，内置 std:hash() 仅提供基本数据类型的哈希值计算
// 数组、对象的哈希值计算需要自行实现
```
=== "Python"