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Started implementing HashTable class
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Kumiho
parent
37b7b83e87
commit
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1
HashTable/.gitignore
vendored
Normal file
1
HashTable/.gitignore
vendored
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@ -0,0 +1 @@
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/bin/
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@ -1,5 +1,9 @@
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package lab;
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import java.io.BufferedReader;
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import java.io.FileNotFoundException;
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import java.io.FileReader;
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import java.io.IOException;
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import java.util.ArrayList;
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import frame.Entry;
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@ -15,6 +19,13 @@ import frame.Entry;
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*/
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public class HashTable {
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private int capacity;
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private int hashFunction; // 0: division, 1: folding, 2: mid_square
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private int probingMode; // 0: linear, 1: quadratic
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private Entry[] data;
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private int valueCount;
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/**
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* The constructor
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@ -33,9 +44,11 @@ public class HashTable {
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* assume a bucket factor of 1.
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*/
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public HashTable(int k, String hashFunction, String collisionResolution) {
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/**
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* Add your code here
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*/
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this.data = new Entry[k];
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this.hashFunction = 0; // TODO
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this.probingMode = collisionResolution.equals("quadratic_probing") ? 1 : 0;
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this.valueCount = 0;
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this.capacity = k;
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}
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/**
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@ -53,10 +66,29 @@ public class HashTable {
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* Hash-Table.
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*/
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public int loadFromFile(String filename) {
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/**
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* Add your code here
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*/
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return 0;
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try (BufferedReader br = new BufferedReader(new FileReader(filename))) {
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String line;
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String[] parts;
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int insertionCount = 0;
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while ((line = br.readLine()) != null) {
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parts = line.split(";");
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Entry entry = new Entry(parts[0], parts[1], parts[2]);
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if(this.insert(entry))
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insertionCount += 1;
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}
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System.out.println(insertionCount);
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return insertionCount;
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} catch (FileNotFoundException e) {
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System.out.println("File not found");
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return 0;
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} catch (IOException e) {
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System.out.println("IO Exception");
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return 0;
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}
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}
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/**
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@ -72,10 +104,28 @@ public class HashTable {
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* if the entry already exists in the Hash-Table
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*/
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public boolean insert(Entry insertEntry) {
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/**
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* Add your code here
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*/
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return false;
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int address = this.getHashAddr(insertEntry);
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int base = address;
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int i = 1;
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while(this.data[address] != null && !this.data[address].isDeleted()) {
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if(i > this.capacity || this.data[address].getKey().equals(insertEntry.getKey()))
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return false;
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address = this.getProbingAddr(base, i);
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i += 1;
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}
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if(this.data[address] == null)
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this.valueCount += 1;
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this.data[address] = insertEntry;
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// Trigger rehash if load factor > 0.75
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if(((double) this.valueCount) / this.capacity > 0.75)
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this.rehash();
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System.out.println("Load: "+Double.toString(((double) this.valueCount) / this.capacity));
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return true;
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}
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/**
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@ -89,10 +139,22 @@ public class HashTable {
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* the entry is not found in the Hash-Table
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*/
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public Entry delete(String deleteKey) {
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/**
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* Add your code here
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*/
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return null;
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int address = this.getHashAddr(deleteKey);
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int base = address;
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int i = 1;
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while(this.data[address] != null && !this.data[address].getKey().equals(deleteKey)) {
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if(i > this.capacity)
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return null;
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address = this.getProbingAddr(base, i);
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i += 1;
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}
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if(this.data[address] != null) {
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this.data[address].markDeleted();
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return this.data[address];
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}
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else
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return null;
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}
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/**
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@ -106,10 +168,17 @@ public class HashTable {
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* null if the entry is not found in the Hash-Table
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*/
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public Entry find(String searchKey) {
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/**
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* Add your code here
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*/
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return null;
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int address = this.getHashAddr(searchKey);
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int base = address;
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int i = 1;
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while(this.data[address] != null && !this.data[address].getKey().equals(searchKey)) {
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if(i > this.capacity)
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return null;
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address = this.getProbingAddr(base, i);
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i += 1;
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}
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return this.data[address].isDeleted() ? null : this.data[address];
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}
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/**
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@ -121,11 +190,44 @@ public class HashTable {
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* @return returns the output Hash-Table in directly interpretable dot code
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*/
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public ArrayList<String> getHashTable() {
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/**
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* Add your code here
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*/
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return null;
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ArrayList<String> dot = new ArrayList<String>();
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dot.add("digraph {");
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dot.add("splines=true;");
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dot.add("nodesep=.01;");
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dot.add("rankdir=LR;");
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dot.add("node[fontsize=8,shape=record,height=.1;]");
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String addressdef = "[fontsize=12,label=\"";
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for(int i = 0; i < this.capacity; i++) {
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addressdef += "<f"+Integer.toString(i)+">"+Integer.toString(i)+(i < this.capacity - 1 ? "|" : "");
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}
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addressdef += "\"];";
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dot.add(addressdef);
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int j = 1;
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for(int i = 0; i < this.capacity; i++) {
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if(this.data[i] != null) {
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String insertSequence = getInsertionSequence(this.data[i].getKey());
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String line = "node"+Integer.toString(j)+"[label=\"{<l>" + this.data[i].getKey() + '|' + this.data[i].getData() + insertSequence + "}\"];";
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dot.add(line);
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System.out.println(line);
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j += 1;
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}
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}
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j = 1;
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for(int i = 0; i < this.capacity; i++) {
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if(this.data[i] != null) {
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String line = "ht:f"+Integer.toString(i)+"->node" + Integer.toString(j) + ":l;";
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dot.add(line);
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System.out.println(line);
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j += 1;
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}
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}
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dot.add("}");
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return dot;
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}
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/**
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* This method increases the capacity of the Hash-Table and reorganizes it, in
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@ -137,8 +239,82 @@ public class HashTable {
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* increased to 1009, which is the closest primary number less than (101*10).
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*/
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private void rehash() {
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/**
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* Add your code here
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*/
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System.out.println("REHASH");
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int newSize = this.capacity * 10;
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while(!isPrime(newSize)) {
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newSize -= 1;
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}
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System.out.println(newSize);
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int oldSize = this.capacity;
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Entry[] oldData = this.data;
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this.data = new Entry[newSize];
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this.capacity = newSize;
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for(int i = 0; i < oldSize; i++) {
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if(oldData[i] != null && !oldData[i].isDeleted()) {
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this.insert(oldData[i]);
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}
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}
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}
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private long decimalRepresentation(String value) {
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char[] key = value.toCharArray();
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String str = Integer.toString((int) key[0]) + Integer.toString((int) key[1]) + Integer.toString((int) key[2]) + Integer.toString((int) key[3]) + Integer.toString((int) key[4]);
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return Long.parseLong(str);
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}
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private int getHashAddr(Entry value) {
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return this.getHashAddr(value.getKey());
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}
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private int getHashAddr(String key) {
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if(this.hashFunction == 0)
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return this.divisionHash(key);
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else
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return 0;
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}
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private int divisionHash(String value) {
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long decimal = decimalRepresentation(value);
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return Math.toIntExact(decimal % this.capacity);
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}
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private int getProbingAddr(int base, int i) {
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if(this.probingMode == 0)
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return (base + i) % this.capacity;
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else {
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int nextTry = ((int)(base - Math.ceil(Math.pow(((float) i)/2, 2))*Math.pow(-1, i))) % this.capacity;
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return nextTry < 0 ? nextTry + this.capacity : nextTry;
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}
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}
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private String getInsertionSequence(String searchKey) {
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int address = this.getHashAddr(searchKey);
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int base = address;
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int i = 1;
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String sequence = "";
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while(this.data[address] != null && !this.data[address].getKey().equals(searchKey)) {
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sequence += Integer.toString(address) + ", ";
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address = this.getProbingAddr(base, i);
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i += 1;
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}
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return sequence.length() > 2 ? "|" + sequence.substring(0, sequence.length() - 2) : "";
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}
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private boolean isPrime(int p) {
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int i = 2;
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while(i <= Math.sqrt(p)) {
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if(p % i == 0)
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return false;
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i++;
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}
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return true;
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}
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}
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