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
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
|
package datastructure;
import java.util.*;
/**
* @author cheysen
* @date 2025/4/3 12:36
* @description B 树是一种树数据结构，它使数据保持排序并允许对数时间的搜索、顺序访问、插入和删除。
* B 树是二叉搜索树的泛化，因为一个节点可以有两个以上的子节点。与自平衡二叉搜索树不同，B 树针对读取和写入大型数据块的系统进行了优化。它通常用于数据库和文件系统。
**/
@SuppressWarnings("unchecked")
public class BTree<T extends Comparable<T>> implements Tree<T> {
//2-3树是最简单的B树:最大key数量2,最大子节点数3,最小key数量2
private int minKeySize = 1;
private int minChildrenSize = minKeySize + 1;
private int maxKeySize = 2 * minKeySize;
private int maxChildrenSize = maxKeySize + 1;
private Node<T> root = null;
private int size = 0;
//默认2-3树
public BTree() {
}
//order:非根节点最少key数量
public BTree(int order) {
this.minKeySize = order;
this.minChildrenSize = minKeySize + 1;
this.maxKeySize = 2 * minKeySize;
this.maxChildrenSize = maxKeySize + 1;
}
public BTree<T> appendAdd(T value) throws Exception {
boolean added = add(value);
if (added) {
return this;
} else {
throw new Exception("add " + value + " error");
}
}
@Override
public boolean add(T value) {
if (root == null) {
root = new Node<T>(null, maxKeySize, maxChildrenSize);
root.addKey(value);
} else {
Node<T> node = root;
while (node != null) {
//没有子节点就在当前节点插入
if (node.numberOfChildren() == 0) {
node.addKey(value);
if (node.numberOfKeys() <= maxKeySize) {
break;
}
//key数量已满，需要分裂
split(node);
break;
}
//否则，按有序的规则查找该插入的节点
T lesser = node.getKey(0);
if (value.compareTo(lesser) <= 0) {
node = node.getChild(0);
continue;
}
int numberOfKeys = node.numberOfKeys();
int last = numberOfKeys - 1;
T greater = node.getKey(last);
if (value.compareTo(greater) > 0) {
node = node.getChild(numberOfKeys);
continue;
}
for (int i = 1; i < node.numberOfKeys(); i++) {
T prev = node.getKey(i - 1);
T next = node.getKey(i);
if (value.compareTo(prev) > 0 && value.compareTo(next) <= 0) {
node = node.getChild(i);
break;
}
}
}
}
size++;
return true;
}
@Override
public T remove(T value) {
T removed = null;
Node<T> node = this.getNode(value);
removed = remove(value, node);
return removed;
}
@Override
public boolean contains(T value) {
Node<T> node = getNode(value);
return node != null;
}
@Override
public void clear() {
root = null;
size = 0;
}
@Override
public int size() {
return size;
}
@Override
public boolean validate() {
if (root == null) {
return true;
}
return validateNode(root);
}
@Override
public Collection<T> toCollection() {
return new JavaCompatibleBTree<>(this);
}
@Override
public String toString() {
return TreePrinter.getString(this);
}
/**
* 获取目标值所在节点
* @param value 要查找的值
* @return 目标值所在节点
*/
private Node<T> getNode(T value) {
Node<T> node = root;
while (node != null) {
//尝试是否比节点最小值小
T lesser = node.getKey(0);
if (value.compareTo(lesser) < 0) {
if (node.numberOfChildren() > 0) {
node = node.getChild(0);
} else {
node = null;
}
continue;
}
//尝试是否比节点最大值大
int numberOfKeys = node.numberOfKeys();
int lastIndex = numberOfKeys - 1;
T greater = node.getKey(lastIndex);
if (value.compareTo(greater) > 0) {
if (node.numberOfChildren() > numberOfKeys) {
node = node.getChild(numberOfKeys);
} else {
node = null;
}
continue;
}
//不满足极大极小情况,在中间值中比较
for (int i = 0; i < numberOfKeys; i++) {
T currentValue = node.getKey(i);
if (currentValue.compareTo(value) == 0) {
return node;
}
int next = i + 1;
if (next <= lastIndex) {
T nextValue = node.getKey(next);
//目标值介于第i与第i+1个key之间时,在第i+1个子节点(如果有)中继续查找
if (value.compareTo(currentValue) > 0 && value.compareTo(nextValue) < 0) {
if (next < node.numberOfChildren()) {
node = node.getChild(next);
break;
}
return null;
}
}
}
}
return null;
}
/**
* 从节点中删除值
* @param value 要删除的值
* @param node 要删除的值所在节点
* @return true-删除成功
*/
private T remove(T value, Node<T> node) {
if (node == null) {
return null;
}
T removed = null;
int index = node.indexOf(value);
removed = node.removeKey(index);
//叶子节点元素的删除:1.直接删除 2.兄弟节点借值 3.合并兄弟节点(之一)与父节点key
if (node.numberOfChildren() == 0) {
if (node.parent != null && node.numberOfKeys() < minKeySize) {
this.combined(node);
} else if (node.parent == null && node.numberOfKeys() == 0) {
//只有一个元素根节点删除,清空树
root = null;
}
} else {
//内部节点元素的删除:1.有序前驱值替换 2.有序后继值替换 3.合并目标值的左右子节点
Node<T> lesser = node.getChild(index);
//找到最大有序前驱
Node<T> greatestNode = this.getGreatestNode(lesser);
T replaceValue = this.removeGreatestValue(greatestNode);
node.addKey(replaceValue);
//借最大有序前驱相当于在子节点中删除一个最大值
if (greatestNode.parent != null && greatestNode.numberOfKeys() < minKeySize) {
this.combined(greatestNode);
}
//combined中不需考虑分裂的情况:借值不用考虑;合并只在左右兄弟节点key数量等于minKeySize时,合并后最大为maxKeySize
//而这里是先借值,再合并,如果是借最有序前驱,假如右兄弟节点有maxKeySize,合并后就需要分裂
if (greatestNode.numberOfChildren() > maxChildrenSize) {
this.split(greatestNode);
}
}
size--;
return removed;
}
/** 当节点key数量不足最小数量时组合父节点和子节点key.组合包括向兄弟节点借值和合并两种情况
* @param node 组合的子节点
* @return true-组合成功
*/
private boolean combined(Node<T> node) {
Node<T> parent = node.parent;
int indexOfParentChild = parent.indexOf(node);
int indexOfLeftNeighbor = indexOfParentChild - 1;
int indexOfRightNeighbor = indexOfParentChild + 1;
Node<T> rightNeighbor = null;
//这里只是初始化
int rightNeighborSize = -minChildrenSize;
//如果有右兄弟节点
if (indexOfRightNeighbor < parent.numberOfChildren()) {
rightNeighbor = parent.getChild(indexOfRightNeighbor);
rightNeighborSize = rightNeighbor.numberOfKeys();
}
//尝试向兄弟节点借值(左右顺序没有先后)
if (rightNeighbor != null && rightNeighborSize > minKeySize) {
//右兄弟节点的最小值
T removeValue = rightNeighbor.getKey(0);
//父节点中有序前驱(相对于给定值而言)的索引
int prev = getIndexOfPreviousValue(parent, removeValue);
T parentValue = parent.removeKey(prev);
T neighborValue = rightNeighbor.removeKey(0);
node.addKey(parentValue);
parent.addKey(neighborValue);
if (rightNeighbor.numberOfChildren() > 0) {
node.addChild(rightNeighbor.removeChild(0));
}
} else {
Node<T> leftNeighbor = null;
int leftNeighborSize = -minChildrenSize;
if (indexOfLeftNeighbor >= 0) {
leftNeighbor = parent.getChild(indexOfLeftNeighbor);
leftNeighborSize = leftNeighbor.numberOfKeys();
}
if (leftNeighbor != null && leftNeighborSize > minKeySize) {
//左兄弟节点的最大值
T removeValue = leftNeighbor.getKey(leftNeighbor.numberOfKeys() - 1);
int nextV = getIndexOfNextValue(parent, removeValue);
T parentValue = parent.removeKey(nextV);
T neighborValue = leftNeighbor.removeKey(leftNeighbor.numberOfKeys() - 1);
node.addKey(parentValue);
parent.addKey(neighborValue);
if (leftNeighbor.numberOfChildren() > 0) {
node.addChild(leftNeighbor.removeChild(leftNeighbor.numberOfChildren() - 1));
}
} else if (rightNeighbor != null && parent.numberOfKeys() > 0) {
//不能借值,尝试与右兄弟节点合并(左右顺序没有先后)
T removeValue = rightNeighbor.getKey(0);
int prev = getIndexOfPreviousValue(parent, removeValue);
T parentValue = parent.removeKey(prev);
parent.removeChild(rightNeighbor);
node.addKey(parentValue);
for (int i = 0; i < rightNeighbor.keySize; i++) {
T v = rightNeighbor.getKey(i);
node.addKey(v);
}
//非叶子节点合并需要考虑
for (int i = 0; i < rightNeighbor.childrenSize; i++) {
Node<T> c = rightNeighbor.getChild(i);
node.addChild(c);
}
if (parent.parent != null && parent.numberOfKeys() < minKeySize) {
//合并使得父节点key数量不足最小数量,继续向上合并
this.combined(parent);
} else if (parent.numberOfKeys() == 0) {
//合并使得父节点没有key,树都高度减少
node.parent = null;
root = node;
}
} else if (leftNeighbor != null && parent.numberOfKeys() > 0) {
T removeValue = leftNeighbor.getKey(leftNeighbor.numberOfKeys() - 1);
int nextV = getIndexOfNextValue(parent, removeValue);
T parentValue = parent.removeKey(nextV);
parent.removeChild(leftNeighbor);
node.addKey(parentValue);
for (int i = 0; i < leftNeighbor.keySize; i++) {
T v = leftNeighbor.getKey(i);
node.addKey(v);
}
for (int i = 0; i < leftNeighbor.childrenSize; i++) {
Node<T> c = leftNeighbor.getChild(i);
node.addChild(c);
}
if (parent.parent != null && parent.numberOfKeys() < minKeySize) {
this.combined(parent);
} else if (parent.numberOfKeys() == 0) {
node.parent = null;
root = node;
}
}
}
return true;
}
/**
* 节点key数量大于最大key数量，从中间分裂
* @param nodeToSplit 要分裂的节点
*/
private void split(Node<T> nodeToSplit) {
Node<T> node = nodeToSplit;
int numberOfKeys = node.numberOfKeys();
int medianIndex = numberOfKeys / 2;//向下取整
T medianValue = node.getKey(medianIndex);
Node<T> left = new Node<>(null, maxKeySize, maxChildrenSize);
for (int i = 0; i < medianIndex; i++) {
left.addKey(node.getKey(i));
}
//如果中间值是第i个key,那么前i个子节点归为分裂出的左节点的子节点
if (node.numberOfChildren() > 0) {
for (int j = 0; j <= medianIndex ; j++) {
Node<T> c = node.getChild(j);
left.addChild(c);
}
}
Node<T> right = new Node<>(null, maxKeySize, maxChildrenSize);
for (int i = medianIndex + 1; i < numberOfKeys ; i++) {
right.addKey(node.getKey(i));
}
//如果中间值是第i个key,那么后m-i个子节点归为分裂出的右节点的子节点
if (node.numberOfChildren() > 0) {
for (int j = medianIndex + 1; j < node.numberOfChildren(); j++) {
Node<T> c = node.getChild(j);
right.addChild(c);
}
}
//将中间值向上弹出至父节点
if (node.parent == null) {
//如果是根节点的分裂,树的高度增加
Node<T> newRoot = new Node<>(null, maxKeySize, maxChildrenSize);
newRoot.addKey(medianValue);
node.parent = newRoot;
root = newRoot;
root.addChild(left);
root.addChild(right);
} else {
Node<T> parent = node.parent;
parent.addKey(medianValue);
parent.removeChild(node);
parent.addChild(left);
parent.addChild(right);
//如果父节点key数量已满,则继续分裂
if (parent.numberOfKeys() > maxKeySize) {
split(parent);
}
}
}
/**
* 在节点中找第一个小于给定值的值的索引
* @param node
* @param value
* @return 有序前驱的索引 | -1
*/
private int getIndexOfPreviousValue(Node<T> node, T value) {
//只有1个值时,直接返回了
for (int i = 1; i < node.numberOfKeys(); i++) {
T t = node.getKey(i);
if (t.compareTo(value) >= 0) {
return i - 1;
}
}
return node.numberOfKeys() - 1;
}
/**
* 在节点中第一个大于给定值的索引
* @param node
* @param value
* @return 有序后继的索引 | -1
*/
private int getIndexOfNextValue(Node<T> node, T value) {
for (int i = 0; i < node.numberOfKeys(); i++) {
T t = node.getKey(i);
if (t.compareTo(value) >= 0) {
return i;
}
}
return node.numberOfKeys() - 1;
}
/**
* 找到给定节点树下的最大(最右)节点
* @param nodeToGet
* @return
*/
private Node<T> getGreatestNode(Node<T> nodeToGet) {
Node<T> node = nodeToGet;
while (node.numberOfChildren() > 0) {
node = node.getChild(node.numberOfChildren() - 1);
}
return node;
}
/**
* 删除节点中的最大值
* @param node
* @return
*/
private T removeGreatestValue(Node<T> node) {
T value = null;
if (node.numberOfKeys() > 0) {
value = node.removeKey(node.numberOfKeys() - 1);
}
return value;
}
/**
* 以给定节点为根节点验证B树是否合法
* @param node
* @return
*/
private boolean validateNode(Node<T> node) {
int keySize = node.numberOfKeys();
if (keySize > 1) {
//验证元素是否升序
for (int i = 1; i < keySize; i++) {
T p = node.getKey(i - 1);
T n = node.getKey(i);
if (p.compareTo(n) > 0) {
return false;
}
}
}
int childrenSize = node.numberOfChildren();
if (node.parent == null) {
//根节点
if (keySize > maxKeySize) {
//根节点没有最小元素限制，空树也视为合法
return false;
} else if (childrenSize == 0) {
return true;
} else if (childrenSize < 2) {
//2-3树是最简单的B树
return false;
} else if (childrenSize > maxChildrenSize) {
return false;
}
} else {
//非根节点
if (keySize < minKeySize) {
return false;
} else if (keySize > maxKeySize) {
return false;
} else if (childrenSize == 0) {
return true;
} else if (keySize != (childrenSize - 1)) {
//key数量可以由子节点树推导，但子节点树不一定是keySize+1
return false;
} else if (childrenSize > maxChildrenSize) {
return false;
} else if (childrenSize < minChildrenSize) {
return false;
}
}
//第一个子节点的有序性
Node<T> first = node.getChild(0);
if (first.getKey(first.numberOfKeys() - 1).compareTo(node.getKey(0)) > 0) {
return false;
}
//最后一个子节点的有序性
Node<T> last = node.getChild(node.numberOfChildren() - 1);
if (last.getKey(0).compareTo(node.getKey(node.numberOfKeys() - 1)) < 0) {
return false;
}
//中间节点的有序性
for (int i = 1; i < node.numberOfKeys(); i++) {
T p = node.getKey(i - 1);
T n = node.getKey(i);
Node<T> c = node.getChild(i);
if (p.compareTo(c.getKey(0)) > 0) {
return false;
}
if (n.compareTo(c.getKey(c.numberOfKeys() - 1)) < 0) {
return false;
}
}
//递归向下验证
for (int i = 0; i < node.childrenSize; i++) {
Node<T> c = node.getChild(i);
boolean valid = this.validateNode(c);
if (!valid) {
return false;
}
}
return true;
}
private static class Node<T extends Comparable<T>> {
private T[] keys = null;
private int keySize = 0;
private Node<T>[] children = null;
private int childrenSize = 0;
private Node<T> parent = null;
private Node(Node<T> parent, int maxKeySize, int maxChildrenSize) {
this.parent = parent;
//+1是为了应对分裂
this.keys = (T[])new Comparable[maxKeySize + 1];
this.children = new Node[maxChildrenSize + 1];
this.keySize = 0;
this.childrenSize = 0;
}
private Comparator<Node<T>> comparator = new Comparator<Node<T>>() {
@Override
public int compare(Node<T> o1, Node<T> o2) {
//TODO 这里该如何定义?
return o1.getKey(0).compareTo(o2.getKey(0));
}
};
private T getKey(int index) {
return keys[index];
}
private int indexOf(T value) {
for (int i = 0; i < keySize; i++) {
if (keys[i].equals(value)) {
return i;
}
}
return -1;
}
private void addKey(T value) {
//不使用排序
int i = 0;
/*通过向后复制来实现插入,如[11,15,20,0,0]插入17
[11,15,20,20,0] -> [11,15,17,20,0]
*/
for (i = keySize - 1; i >=0 && value.compareTo(keys[i]) < 0 ; i--) {
keys[i + 1] = keys[i];
}
keys[i + 1] = value;
keySize++;
//使用排序
/*
keys[keysSize++] = value;
Arrays.sort(keys, 0, keysSize);
*/
}
//此方法只考虑节点内部元素的删除
private T removeKey(T value) {
T removed = null;
boolean found = false;
if (keySize == 0) {
return null;
}
for (int i = 0; i < keySize; i++) {
if (keys[i].equals(value)) {
found = true;
removed = keys[i];
} else if (found) {
//向前复制删除,第一次循环不会进入这段逻辑,所以i-1>0
keys[i -1 ] = keys[i];
}
}
//删除相当于整体向前移一位
if (found) {
keySize--;
keys[keySize] = null;
}
return null;
}
//此方法只考虑节点内部元素的删除
private T removeKey(int index) {
if (index >= keySize) {
return null;
}
T value = keys[index];
for (int i = index + 1; i < keySize; i++) {
keys[i - 1] = keys[i];
}
keySize--;
keys[keySize] = null;
return value;
}
private int numberOfKeys() {
return keySize;
}
private int numberOfChildren() {return childrenSize;}
private Node<T> getChild(int index) {
if (index >= childrenSize) {
return null;
}
return children[index];
}
private int indexOf(Node<T> child) {
for (int i = 0; i < childrenSize; i++) {
if (children[i].equals(child)) {
return i;
}
}
return -1;
}
private boolean addChild(Node<T> child) {
child.parent = this;
children[childrenSize++] = child;
Arrays.sort(children, 0, childrenSize, comparator);
return true;
}
private boolean removeChild(Node<T> child) {
boolean found = false;
if (childrenSize == 0) {
return found;
}
for (int i = 0; i < childrenSize; i++) {
if (children[i].equals(child)) {
found = true;
} else if(found) {
children[i - 1] = children[i];
}
}
if (found) {
childrenSize--;
children[childrenSize] = null;
}
return found;
}
private Node<T> removeChild(int index) {
if (index >= childrenSize) {
return null;
}
Node<T> value = children[index];
children[index] = null;
for (int i = index + 1; i < childrenSize; i++) {
children[i - 1] = children[i];
}
childrenSize--;
children[childrenSize] = null;
return value;
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder();
builder.append("keys=[");
for (int i = 0; i < numberOfKeys(); i++) {
T value = getKey(i);
builder.append(value);
if (i < numberOfKeys() - 1) {
builder.append(", ");
}
}
builder.append("]\n");
if (parent != null) {
builder.append("parent=[");
for (int i = 0; i < parent.numberOfKeys(); i++) {
T value = parent.getKey(i);
builder.append(value);
if (i < parent.numberOfKeys() - 1) {
builder.append(", ");
}
builder.append(", ");
}
}
if (children != null) {
builder.append("keySize=")
.append(numberOfKeys())
.append(" children=[")
.append(numberOfChildren()).append("\n");
}
return builder.toString();
}
}
public static class JavaCompatibleBTree<T extends Comparable<T>> extends AbstractCollection<T> {
private BTree<T> tree = null;
public JavaCompatibleBTree(BTree<T> tree) {
this.tree = tree;
}
@Override
public boolean add(T value) {
return tree.add(value);
}
@Override
public boolean remove(Object value) {
return tree.remove((T) value) != null;
}
@Override
public boolean contains(Object value) {
return tree.contains((T) value);
}
@Override
public int size() {
return tree.size();
}
@Override
public Iterator<T> iterator() {
return new BTreeIterator<>(this.tree);
}
private static class BTreeIterator<C extends Comparable<C>> implements Iterator<C> {
private BTree<C> tree = null;
private BTree.Node<C> lastNode = null;
private C lastValue = null;
private int index = 0;
private Deque<BTree.Node<C>> toVisit = new ArrayDeque<>();
public BTreeIterator(BTree<C> tree) {
this.tree = tree;
if (tree.root != null && tree.root.keySize > 0) {
toVisit.add(tree.root);
}
}
@Override
public boolean hasNext() {
if ((lastNode != null && index < lastNode.keySize) || toVisit.size() > 0) {
return true;
}
return false;
}
@Override
public C next() {
if (lastNode != null && (index < lastNode.keySize)) {
lastValue = lastNode.getKey(index++);
return lastValue;
}
if (toVisit.size() > 0) {
Node<C> n = toVisit.pop();
for (int i = 0; i < n.childrenSize; i++) {
toVisit.add(n.getChild(i));
}
index = 0;
lastNode = n;
lastValue = lastNode.getKey(index++);
return lastValue;
}
return null;
}
@Override
public void remove() {
if (lastNode != null && lastValue != null) {
//删除时，重置迭代器（效率很低）
tree.remove(lastValue, lastNode);
lastNode = null;
lastValue = null;
index = 0;
toVisit.clear();
if (tree.root != null && tree.root.keySize > 0) {
toVisit.add(tree.root);
}
}
}
}
}
private static class TreePrinter {
public static <T extends Comparable<T>> String getString(BTree<T> tree) {
if (tree.root == null) {
return "Tree is empty";
}
return getString(tree.root, "", true);
}
private static <T extends Comparable<T>> String getString(Node<T> node, String prefix, boolean isTail) {
StringBuilder builder = new StringBuilder();
builder.append(prefix).append(isTail ? "└── " : "├── ");
for (int i = 0; i < node.numberOfKeys(); i++) {
T value = node.getKey(i);
builder.append(value);
if (i < node.numberOfKeys() - 1) {
builder.append(", ");
}
}
builder.append("\n");
if (node.children != null) {
for (int i = 0; i < node.numberOfChildren() - 1; i++) {
Node<T> obj = node.getChild(i);
builder.append(getString(obj, prefix + (isTail ? " " : "| "), false));
}
if (node.numberOfChildren() >=1 ) {
Node<T> obj = node.getChild(node.numberOfChildren() - 1);
builder.append(getString(obj, prefix + (isTail ? " " : "| "), true));
}
}
return builder.toString();
}
}
public static void main(String[] args) throws Exception {
BTree<Integer> tbTree = new BTree<>(1);
tbTree.add(12);
tbTree.add(23);
tbTree.add(6);
tbTree.add(8);
tbTree.add(15);
tbTree.add(19);
tbTree.add(45);
tbTree.add(1);
tbTree.add(4);
tbTree.add(7);
tbTree.add(5);
System.out.println(tbTree);
tbTree.toCollection().forEach(System.out::println);
BTree<Integer> fiveWay = new BTree<>(2);
fiveWay.appendAdd(78)
.appendAdd(22)
.appendAdd(75)
.appendAdd(89)
.appendAdd(94)
.appendAdd(10)
.appendAdd(12)
.appendAdd(23)
.appendAdd(31)
.appendAdd(76)
.appendAdd(77)
.appendAdd(86)
.appendAdd(87)
.appendAdd(88)
.appendAdd(90)
.appendAdd(93)
.appendAdd(98)
.appendAdd(99);
System.out.println(fiveWay);
fiveWay.remove(22);
System.out.println(fiveWay);
fiveWay.toCollection().forEach(System.out::println);
}
}
|
