Hash-Tabelle: Lösung zu Aufgabenteil (a)

20180430/hash_table_sura.cpp

+
+#include <iostream>
+#include <string>
+
+using namespace std;
+
+template <typename argtype>
+class HashTable
+{
+	private:
+		class HashEntry
+		{
+			private:
+				string key;
+				argtype value;
+	
+			public:
+				HashEntry (string key, argtype value)
+				{
+					this->key = key;
+					this->value = value;
+				}
+
+				string getKey () { return key; }
+				argtype getValue () { return value; }
+		};
+		
+		HashEntry **table;
+		int size;
+		
+		// Create numerical representation of a string
+		int calcHash (string key)
+		{
+			int num = 0;
+
+			for (string::iterator it = key.begin(); it != key.end(); it++)
+			{
+				num += int (*it);
+			}
+			
+			return num;
+		}
+		
+	public:
+		// Initialize table
+		HashTable (int size)
+		{
+			this->size = size;
+			this->table = new HashEntry *[size];
+			
+			for (int i = 0; i < size; i++)
+			{
+				table[i] = NULL;
+			}
+		}
+
+		// Get element by key
+		argtype get (string key)
+		{
+			int keyHash = calcHash(key);
+			int hash = (keyHash % size);
+			
+			// prevent using same table slot multiple times
+			while (table[hash] != NULL && table[hash]->getKey() != key)
+				hash = (hash + 1) % size;
+			
+			if (table[hash] == NULL)
+				return NULL;
+			else
+				return table[hash]->getValue();
+		}
+
+		// Add element to table
+		void put (string key, argtype value)
+		{
+			int keyHash = calcHash (key);
+			int hash = (keyHash % size);
+			
+			// prevent using same table slot multiple times
+			while (table[hash] != NULL && table[hash]->getKey() != key)
+				hash = (hash + 1) % size;
+			
+			if (table[hash] != NULL)
+				delete table[hash];
+			
+			table[hash] = new HashEntry (key, value);
+		}
+
+		// Destructor
+		~HashTable ()
+		{
+			for (int i = 0; i < size; i++)
+			{
+				if (table[i] != NULL)
+					delete table[i];
+			}
+			
+			delete[] table;
+		}
+};
+
+int main ()
+{
+	HashTable <string> str_table (4);
+	str_table.put("author", "Martin Sura");
+	str_table.put("date", "29.04.2018");
+	str_table.put("version", "1.0");
+	str_table.put("comment", "Hash table using own implementation.");
+	
+	HashTable <int> int_table (4);
+	int_table.put("author", 1);
+	int_table.put("date", 2);
+	int_table.put("version", 3);
+	int_table.put("comment", 4);
+	
+	cout << "Hash Table with string content: " << endl;
+	cout << "author: " << str_table.get("author") << endl;
+	cout << "date: " << str_table.get("date") << endl;
+	cout << "version: " << str_table.get("version") << endl;
+	cout << "comment: " << str_table.get("comment") << endl;
+
+	cout << "\nHash Table with int content: " << endl;
+	cout << "author: " << int_table.get("author") << endl;
+	cout << "date: " << int_table.get("date") << endl;
+	cout << "version: " << int_table.get("version") << endl;
+	cout << "comment: " << int_table.get("comment") << endl;
+
+	return 0;
+}