Week 13: Assignment - Hash Tables
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cmake_minimum_required(VERSION 3.16)
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project(week-13)
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set(CMAKE_CXX_STANDARD 14)
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add_executable(week-13 main.cpp)
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/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
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* Champlain College SDEV-345-81
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*
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* C++ Week 13: Hash Tables - (2020/12/06)
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*
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* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
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*
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* Write a menu driven program that creates a hash table using an array.
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* The program should give the user the following options and should run in an infinite loop:
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* 1) Insert key
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* 2) Delete key
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* 3) Display hash table
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* 4) Find key
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* The key should be a string and the program should calculate the location using a hash function.
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* The program should also prompt the user when there is a collision and when the hash table is full.
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*
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* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
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*
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* Written by Llewellyn van der Merwe <llewellyn.vandermerw@mymail.champlain.edu>, December 2020
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* Copyright (C) 2020. All Rights Reserved
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* License GNU/GPL Version 2 or later - http://www.gnu.org/licenses/gpl-2.0.html
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*
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* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
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// Based on the examples from Paul Programming series on Hash tables
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// https://www.youtube.com/playlist?list=PLTxllHdfUq4f7-uHOpxXnBUbsuLiI9pmb
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#include <iostream>
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#include <string>
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#include <limits>
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using namespace std;
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class HashTable{
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private:
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// never use this as a value ;)
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const string emptyString = "|//_-++-_0.^.0_-++-_\\|";
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// the size of the array
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static const int tableSize = 5;
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// the node to store in hash table array
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struct node{
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string value;
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node* next;
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};
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// the HashBucket table array of nodes
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node* HashBucket[tableSize];
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// search for value in table
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bool find(string &value){
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// get the HashBucket value of the string
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int key = Hash(value);
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// continue the search
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return find(key, value);
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}
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// smart search by key and value
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bool find(int &key, string &value){
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// check if the HashBucket has a collision
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if (HashBucket[key]->value == value){
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// found
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return true;
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} else if (HashBucket[key]->next != nullptr) {
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// continue the search
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return find(HashBucket[key]->next, value);
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}
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return false;
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}
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// smart search in node with value
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bool find(node* bucket, string &value){
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// check if the value is found
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if (bucket->value == value){
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// found
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return true;
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} else if (bucket->next != nullptr) {
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// continue the search
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return find(bucket->next, value);
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}
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// value is not found
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return false;
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}
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// display each bucket
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void display(node* bucket){
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// print out the value
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cout << bucket->value;
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// loop over all the buckets
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if (bucket->next != nullptr) {
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cout << "; "; // little spacer :)
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display(bucket->next);
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}
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}
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public:
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// our constructor of our HashBucket table
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HashTable(){
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// initialize the empty HashBucket tables
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for(int i = 0; i < tableSize; i++) {
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HashBucket[i] = new node;
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HashBucket[i]->value = emptyString;
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HashBucket[i]->next = nullptr;
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}
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};
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// our destructor of our HashBucket table
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~HashTable(){
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}
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// our HashBucket function
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int Hash(string key) {
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int hash = 0;
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int tmp = key.length();
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// now loop the string value-key to get HashBucket
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for (int i = 0; i < tmp; i++) {
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hash = hash + (int) key[i];
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}
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// return the remainder
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return hash % tableSize;
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}
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// add a node value
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void insert(string value)
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{
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// get the HashBucket value of the string
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int key = Hash(value);
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// check if the HashBucket has a collision
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if (HashBucket[key]->value == emptyString){
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// give success adding info
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cout << "█ [Info] " << value << " - added successfully." << endl;
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// new value
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HashBucket[key]->value = value;
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} else {
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// get the first item
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node *firstNode = HashBucket[key];
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// check if the values are the same
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if(!find(firstNode, value)) {
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// prom the user if we should add to bucket
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cout << "█ [Warning] Collision detected." << endl;
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cout << "█ Do you still want to add: " << value << endl;
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cout << "█ Enter initial [yes/no]: ";
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char choice;
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cin >> choice;
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if (choice == 'y' || choice == 'Y') {
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// give collision warning
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cout << "██████████████████████████████████████████████████████████" << endl;
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cout << "█ Collision resolved!" << endl;
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cout << "█ [Info] " << value << " - added amicably." << endl;
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// create a new node
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node *newNode = new node;
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newNode->value = value;
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newNode->next = firstNode;
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// add the new node
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HashBucket[key] = newNode;
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} else {
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// give notice
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cout << "█ [Notice] " << value << " - not added." << endl;
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}
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} else {
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// give collision error
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cout << "█ [Error] " << value << " - exists." << endl;
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}
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}
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cout << "██████████████████████████████████████████████████████████" << endl;
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return;
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}
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// search if the value is in the hash table
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void search(string &value){
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// use the find method/function
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if (find(value)){
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cout << "█ [Success] " << value << " - found" << endl;
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} else {
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cout << "█ [Notice] " << value << " - not found" << endl;
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}
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cout << "██████████████████████████████████████████████████████████" << endl;
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return;
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}
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// display the hash table
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void display(){
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cout << "███ THE HASH TABLE BUCKETS ██████████████████████████████" << endl;
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cout << "██████████████████████████████████████████████████████████" << endl;
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// loop over all the buckets
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int tableFull = 0;
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for(int i = 0; i < tableSize; i++) {
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// only print out if bucket has values
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if (HashBucket[i]->value != emptyString) {
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cout << "█ Bucket Nr: " << i << " {";
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display(HashBucket[i]);
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cout << "}" << endl;
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cout << "██████████████████████████████████████████████████████████" << endl;
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tableFull++;
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} else {
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// empty notice
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cout << "█ Bucket Nr: " << i << " is empty" << endl;
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cout << "██████████████████████████████████████████████████████████" << endl;
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}
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}
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if (tableSize == tableFull){
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cout << "███ EACH TABLE BUCKET HAS A VALUE ████████████████████████" << endl;
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} else {
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cout << "███ TABLE BUCKETS NOT FULL ███████████████████████████████" << endl;
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}
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return;
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}
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// delete a value from the table
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void remove(string value){
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// get the HashBucket value of the string
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int key = Hash(value);
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// the table does not have this value
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if (HashBucket[key]->value == emptyString) {
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// not found notice
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cout << "█ [Notice] " << value << " - not found." << endl;
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}
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// last value added to bucket is a match
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else if (HashBucket[key]->value == value && HashBucket[key]->next == nullptr){
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// remove the value
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HashBucket[key]->value = emptyString;
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// removed notice
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cout << "█ [Success] " << value << " - removed." << endl;
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}
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// last value added to bucket is a match but there is more nodes
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else if (HashBucket[key]->value == value){
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// get the last node
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node* delPtr = HashBucket[key];
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// move the next node up
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HashBucket[key] = delPtr->next;
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// remove the last added value
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delete delPtr;
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// removed notice
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cout << "█ [Success] " << value << " - removed." << endl;
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} else {
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// some tmp pointers
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node* P1 = HashBucket[key];
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node* P2 = HashBucket[key]->next;
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// lets start the search
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while (P1 != nullptr && P1->value != value) {
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// no match found, and not at end yet
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P2 = P1;
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P1 = P1->next;
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}
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// if no match was found
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if (P1 == nullptr) {
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// not found notice
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cout << "█ [Notice] " << value << " - not found." << endl;
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}
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// so seems like value is found
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else {
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// set the node to delete
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node* delPtr = P1;
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// do the swap
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P1 = P1->next;
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P2->next = P1;
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// remove the last added value
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delete delPtr;
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// removed notice
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cout << "█ [Success] " << value << " - removed." << endl;
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}
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}
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cout << "██████████████████████████████████████████████████████████" << endl;
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return;
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}
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};
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int main (){
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// instantiate the table
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HashTable Table;
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// program loop (taken and adapted from this weeks module)
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char choice = 'b';
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string aKey;
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// start the program
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cout << "██████████████████████████████████████████████████████████" << endl;
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// interact with user
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while(choice != 'x')
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{
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cout << "█ Enter first letter of "
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<< "show, insert, delete, or find: ";
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char choice;
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cin >> choice;
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// clear cin stream
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cin.clear();
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cin.ignore(numeric_limits<streamsize>::max(), '\n');
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switch(choice)
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{
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case 's':
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Table.display();
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break;
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case 'i':
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cout << "█ Enter key value to insert: ";
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getline( cin, aKey );
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// now insert the string
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Table.insert(aKey);
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break;
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case 'd':
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cout << "█ Enter key value to delete: ";
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getline( cin, aKey );
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// now remove the string
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Table.remove(aKey);
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break;
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case 'f':
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cout << "█ Enter key value to find: ";
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getline( cin, aKey );
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// now search for the string
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Table.search(aKey);
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break;
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default:
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cout << "█ Invalid entry\n";
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break;
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}
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}
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}
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