-
Notifications
You must be signed in to change notification settings - Fork 292
/
SeparateChainingHashSet.cs
316 lines (243 loc) · 7.89 KB
/
SeparateChainingHashSet.cs
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
using System;
using System.Collections;
using System.Collections.Generic;
namespace Advanced.Algorithms.DataStructures.Foundation;
internal class SeparateChainingHashSet<T> : IHashSet<T>
{
private const double Tolerance = 0.1;
private readonly int initialBucketSize;
private int filledBuckets;
private DoublyLinkedList<HashSetNode<T>>[] hashArray;
internal SeparateChainingHashSet(int initialBucketSize = 3)
{
this.initialBucketSize = initialBucketSize;
hashArray = new DoublyLinkedList<HashSetNode<T>>[initialBucketSize];
}
private int BucketSize => hashArray.Length;
public int Count { get; private set; }
public bool Contains(T value)
{
var index = Math.Abs(value.GetHashCode()) % BucketSize;
if (hashArray[index] == null) return false;
var current = hashArray[index].Head;
while (current != null)
{
if (current.Data.Value.Equals(value)) return true;
current = current.Next;
}
return false;
}
public void Add(T value)
{
Grow();
var index = Math.Abs(value.GetHashCode()) % BucketSize;
if (hashArray[index] == null)
{
hashArray[index] = new DoublyLinkedList<HashSetNode<T>>();
hashArray[index].InsertFirst(new HashSetNode<T>(value));
filledBuckets++;
}
else
{
var current = hashArray[index].Head;
while (current != null)
{
if (current.Data.Value.Equals(value)) throw new Exception("Duplicate value");
current = current.Next;
}
hashArray[index].InsertFirst(new HashSetNode<T>(value));
}
Count++;
}
public void Remove(T value)
{
var index = Math.Abs(value.GetHashCode()) % BucketSize;
if (hashArray[index] == null) throw new Exception("No such item for given value");
var current = hashArray[index].Head;
//TODO merge both search and remove to a single loop here!
DoublyLinkedListNode<HashSetNode<T>> item = null;
while (current != null)
{
if (current.Data.Value.Equals(value))
{
item = current;
break;
}
current = current.Next;
}
//remove
if (item == null)
{
throw new Exception("No such item for given value");
}
hashArray[index].Delete(item);
//if list is empty mark bucket as null
if (hashArray[index].Head == null)
{
hashArray[index] = null;
filledBuckets--;
}
Count--;
Shrink();
}
public void Clear()
{
hashArray = new DoublyLinkedList<HashSetNode<T>>[initialBucketSize];
Count = 0;
filledBuckets = 0;
}
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
public IEnumerator<T> GetEnumerator()
{
return new SeparateChainingHashSetEnumerator<T>(hashArray, BucketSize);
}
private void SetValue(T value)
{
var index = Math.Abs(value.GetHashCode()) % BucketSize;
if (hashArray[index] == null) throw new Exception("Item not found");
var current = hashArray[index].Head;
while (current != null)
{
if (current.Data.Value.Equals(value))
{
Remove(value);
Add(value);
return;
}
current = current.Next;
}
throw new Exception("Item not found");
}
private void Grow()
{
if (filledBuckets >= BucketSize * 0.7)
{
filledBuckets = 0;
//increase array size exponentially on demand
var newBucketSize = BucketSize * 2;
var biggerArray = new DoublyLinkedList<HashSetNode<T>>[newBucketSize];
for (var i = 0; i < BucketSize; i++)
{
var item = hashArray[i];
//hashcode changes when bucket size changes
if (item != null)
if (item.Head != null)
{
var current = item.Head;
//find new location for each item
while (current != null)
{
var next = current.Next;
var newIndex = Math.Abs(current.Data.Value.GetHashCode()) % newBucketSize;
if (biggerArray[newIndex] == null)
{
filledBuckets++;
biggerArray[newIndex] = new DoublyLinkedList<HashSetNode<T>>();
}
biggerArray[newIndex].InsertFirst(current);
current = next;
}
}
}
hashArray = biggerArray;
}
}
private void Shrink()
{
if (Math.Abs(filledBuckets - BucketSize * 0.3) < Tolerance && BucketSize / 2 > initialBucketSize)
{
filledBuckets = 0;
//reduce array by half
var newBucketSize = BucketSize / 2;
var smallerArray = new DoublyLinkedList<HashSetNode<T>>[newBucketSize];
for (var i = 0; i < BucketSize; i++)
{
var item = hashArray[i];
//hashcode changes when bucket size changes
if (item?.Head != null)
{
var current = item.Head;
//find new location for each item
while (current != null)
{
var next = current.Next;
var newIndex = Math.Abs(current.Data.Value.GetHashCode()) % newBucketSize;
if (smallerArray[newIndex] == null)
{
filledBuckets++;
smallerArray[newIndex] = new DoublyLinkedList<HashSetNode<T>>();
}
smallerArray[newIndex].InsertFirst(current);
current = next;
}
}
}
hashArray = smallerArray;
}
}
}
internal class SeparateChainingHashSetEnumerator<T> : IEnumerator<T>
{
private DoublyLinkedListNode<HashSetNode<T>> currentNode;
internal DoublyLinkedList<HashSetNode<T>>[] HashList;
private int length;
// Enumerators are positioned before the first element
// until the first MoveNext() call.
private int position = -1;
internal SeparateChainingHashSetEnumerator(DoublyLinkedList<HashSetNode<T>>[] hashList, int length)
{
this.length = length;
this.HashList = hashList;
}
public bool MoveNext()
{
if (currentNode?.Next != null)
{
currentNode = currentNode.Next;
return true;
}
while (currentNode?.Next == null)
{
position++;
if (position < length)
{
if (HashList[position] == null)
continue;
currentNode = HashList[position].Head;
if (currentNode == null)
continue;
return true;
}
break;
}
return false;
}
public void Reset()
{
position = -1;
currentNode = null;
}
object IEnumerator.Current => Current;
public T Current
{
get
{
try
{
return currentNode.Data.Value;
}
catch (IndexOutOfRangeException)
{
throw new InvalidOperationException();
}
}
}
public void Dispose()
{
length = 0;
HashList = null;
}
}