|
1 |
| -package com.baeldung.algorithms.minheapmerge; |
2 |
| - |
3 |
| -public class MinHeap { |
4 |
| - |
5 |
| - HeapNode[] heapNodes; |
6 |
| - |
7 |
| - public MinHeap(HeapNode heapNodes[]) { |
8 |
| - this.heapNodes = heapNodes; |
9 |
| - heapifyFromLastLeafsParent(); |
10 |
| - } |
11 |
| - |
12 |
| - void heapifyFromLastLeafsParent() { |
13 |
| - int lastLeafsParentIndex = getParentNodeIndex(heapNodes.length); |
14 |
| - while (lastLeafsParentIndex >= 0) { |
15 |
| - heapify(lastLeafsParentIndex); |
16 |
| - lastLeafsParentIndex--; |
17 |
| - } |
18 |
| - } |
19 |
| - |
20 |
| - void heapify(int index) { |
21 |
| - int leftNodeIndex = getLeftNodeIndex(index); |
22 |
| - int rightNodeIndex = getRightNodeIndex(index); |
23 |
| - int smallestElementIndex = index; |
24 |
| - if (leftNodeIndex < heapNodes.length && heapNodes[leftNodeIndex].element < heapNodes[index].element) { |
25 |
| - smallestElementIndex = leftNodeIndex; |
26 |
| - } |
27 |
| - if (rightNodeIndex < heapNodes.length && heapNodes[rightNodeIndex].element < heapNodes[smallestElementIndex].element) { |
28 |
| - smallestElementIndex = rightNodeIndex; |
29 |
| - } |
30 |
| - if (smallestElementIndex != index) { |
31 |
| - swap(index, smallestElementIndex); |
32 |
| - heapify(smallestElementIndex); |
33 |
| - } |
34 |
| - } |
35 |
| - |
36 |
| - int getParentNodeIndex(int index) { |
37 |
| - return (index - 1) / 2; |
38 |
| - } |
39 |
| - |
40 |
| - int getLeftNodeIndex(int index) { |
41 |
| - return (2 * index + 1); |
42 |
| - } |
43 |
| - |
44 |
| - int getRightNodeIndex(int index) { |
45 |
| - return (2 * index + 2); |
46 |
| - } |
47 |
| - |
48 |
| - HeapNode getRootNode() { |
49 |
| - return heapNodes[0]; |
50 |
| - } |
51 |
| - |
52 |
| - void heapifyFromRoot() { |
53 |
| - heapify(0); |
54 |
| - } |
55 |
| - |
56 |
| - void swap(int i, int j) { |
57 |
| - HeapNode temp = heapNodes[i]; |
58 |
| - heapNodes[i] = heapNodes[j]; |
59 |
| - heapNodes[j] = temp; |
60 |
| - } |
61 |
| - |
62 |
| - static int[] merge(int[][] array) { |
63 |
| - HeapNode[] heapNodes = new HeapNode[array.length]; |
64 |
| - int resultingArraySize = 0; |
65 |
| - |
66 |
| - for (int i = 0; i < array.length; i++) { |
67 |
| - HeapNode node = new HeapNode(array[i][0], i); |
68 |
| - heapNodes[i] = node; |
69 |
| - resultingArraySize += array[i].length; |
70 |
| - } |
71 |
| - |
72 |
| - MinHeap minHeap = new MinHeap(heapNodes); |
73 |
| - int[] resultingArray = new int[resultingArraySize]; |
74 |
| - |
75 |
| - for (int i = 0; i < resultingArraySize; i++) { |
76 |
| - HeapNode root = minHeap.getRootNode(); |
77 |
| - resultingArray[i] = root.element; |
78 |
| - |
79 |
| - if (root.nextElementIndex < array[root.arrayIndex].length) { |
80 |
| - root.element = array[root.arrayIndex][root.nextElementIndex++]; |
81 |
| - } else { |
82 |
| - root.element = Integer.MAX_VALUE; |
83 |
| - } |
84 |
| - minHeap.heapifyFromRoot(); |
85 |
| - } |
86 |
| - return resultingArray; |
87 |
| - } |
88 |
| -} |
| 1 | +package com.baeldung.algorithms.minheapmerge; |
| 2 | + |
| 3 | +public class MinHeap { |
| 4 | + |
| 5 | + HeapNode[] heapNodes; |
| 6 | + |
| 7 | + public MinHeap(HeapNode heapNodes[]) { |
| 8 | + this.heapNodes = heapNodes; |
| 9 | + heapifyFromLastLeafsParent(); |
| 10 | + } |
| 11 | + |
| 12 | + void heapifyFromLastLeafsParent() { |
| 13 | + int lastLeafsParentIndex = getParentNodeIndex(heapNodes.length); |
| 14 | + while (lastLeafsParentIndex >= 0) { |
| 15 | + heapify(lastLeafsParentIndex); |
| 16 | + lastLeafsParentIndex--; |
| 17 | + } |
| 18 | + } |
| 19 | + |
| 20 | + void heapify(int index) { |
| 21 | + int leftNodeIndex = getLeftNodeIndex(index); |
| 22 | + int rightNodeIndex = getRightNodeIndex(index); |
| 23 | + int smallestElementIndex = index; |
| 24 | + if (leftNodeIndex < heapNodes.length && heapNodes[leftNodeIndex].element < heapNodes[index].element) { |
| 25 | + smallestElementIndex = leftNodeIndex; |
| 26 | + } |
| 27 | + if (rightNodeIndex < heapNodes.length && heapNodes[rightNodeIndex].element < heapNodes[smallestElementIndex].element) { |
| 28 | + smallestElementIndex = rightNodeIndex; |
| 29 | + } |
| 30 | + if (smallestElementIndex != index) { |
| 31 | + swap(index, smallestElementIndex); |
| 32 | + heapify(smallestElementIndex); |
| 33 | + } |
| 34 | + } |
| 35 | + |
| 36 | + int getParentNodeIndex(int index) { |
| 37 | + return (index - 1) / 2; |
| 38 | + } |
| 39 | + |
| 40 | + int getLeftNodeIndex(int index) { |
| 41 | + return (2 * index + 1); |
| 42 | + } |
| 43 | + |
| 44 | + int getRightNodeIndex(int index) { |
| 45 | + return (2 * index + 2); |
| 46 | + } |
| 47 | + |
| 48 | + HeapNode getRootNode() { |
| 49 | + return heapNodes[0]; |
| 50 | + } |
| 51 | + |
| 52 | + void heapifyFromRoot() { |
| 53 | + heapify(0); |
| 54 | + } |
| 55 | + |
| 56 | + void swap(int i, int j) { |
| 57 | + HeapNode temp = heapNodes[i]; |
| 58 | + heapNodes[i] = heapNodes[j]; |
| 59 | + heapNodes[j] = temp; |
| 60 | + } |
| 61 | + |
| 62 | + static int[] merge(int[][] array) { |
| 63 | + HeapNode[] heapNodes = new HeapNode[array.length]; |
| 64 | + int resultingArraySize = 0; |
| 65 | + |
| 66 | + for (int i = 0; i < array.length; i++) { |
| 67 | + HeapNode node = new HeapNode(array[i][0], i); |
| 68 | + heapNodes[i] = node; |
| 69 | + resultingArraySize += array[i].length; |
| 70 | + } |
| 71 | + |
| 72 | + MinHeap minHeap = new MinHeap(heapNodes); |
| 73 | + int[] resultingArray = new int[resultingArraySize]; |
| 74 | + |
| 75 | + for (int i = 0; i < resultingArraySize; i++) { |
| 76 | + HeapNode root = minHeap.getRootNode(); |
| 77 | + resultingArray[i] = root.element; |
| 78 | + |
| 79 | + if (root.nextElementIndex < array[root.arrayIndex].length) { |
| 80 | + root.element = array[root.arrayIndex][root.nextElementIndex++]; |
| 81 | + } else { |
| 82 | + root.element = Integer.MAX_VALUE; |
| 83 | + } |
| 84 | + minHeap.heapifyFromRoot(); |
| 85 | + } |
| 86 | + return resultingArray; |
| 87 | + } |
| 88 | +} |
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