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

codes/cpp/chapter_hashing/built_in_hash.cpp

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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
+}

codes/cpp/chapter_hashing/simple_hash.cpp

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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;
+}