rename tree lectures

lectures/23_hash_tables_I/hash_phonebook_code.cpp

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+
+
+int hash_function(int number) {
+  //return 5;                    /// BAD: always the same
+  //return number / 1000000000;  /// BAD: first bad
+  return number % PHONEBOOK_SIZE;  // REASONABLY GOOD:
+}
+
+void add(Node* phonebook[PHONEBOOK_SIZE], int number, const std::string& name) {
+  int index = hash_function(number) % PHONEBOOK_SIZE;
+  Node* tmp = new Node;
+  tmp->name = name;
+  tmp->number = number;
+  tmp->next = phonebook[index];
+  phonebook[index] = tmp;
+  // what about duplicate / repeated add?
+}
+
+std::string identify(Node* phonebook[PHONEBOOK_SIZE], int number) {
+  Node* current =  phonebook[ hash_function(number) % PHONEBOOK_SIZE ];
+  while ( current != NULL && current->number != number ) {
+    current = current->next;
+  }
+  if (current == NULL) return "UNKNOWN CALLER";
+  return current->name;
+}