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comparison src/org/tmatesoft/hg/internal/ArrayHelper.java @ 307:2f2ab5c27f41

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Collect sort reverse indexes along with array sorting
author Artem Tikhomirov <tikhomirov.artem@gmail.com>
date Sat, 24 Sep 2011 04:06:27 +0200
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children 237de162be28
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306:971baa95fb07 307:2f2ab5c27f41
1 /*
2 * Copyright (c) 2011 TMate Software Ltd
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; version 2 of the License.
7 *
8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 * GNU General Public License for more details.
12 *
13 * For information on how to redistribute this software under
14 * the terms of a license other than GNU General Public License
15 * contact TMate Software at support@hg4j.com
16 */
17 package org.tmatesoft.hg.internal;
18
19 /**
20 *
21 * @author Artem Tikhomirov
22 * @author TMate Software Ltd.
23 */
24 public class ArrayHelper {
25 private int[] reverse;
26
27 @SuppressWarnings("unchecked")
28 public void sort(Comparable<?>[] a) {
29 // Object[] aux = (Object[]) a.clone();
30 reverse = new int[a.length];
31 sort1((Comparable<Object>[])a, 0, a.length);
32 }
33
34 private void sort1(Comparable<Object> x[], int off, int len) {
35 // Insertion sort on smallest arrays
36 if (len < 7) {
37 for (int i=off; i<len+off; i++)
38 for (int j=i; j>off && x[j-1].compareTo(x[j]) > 0; j--)
39 swap(x, j, j-1);
40 return;
41 }
42
43 // Choose a partition element, v
44 int m = off + (len >> 1); // Small arrays, middle element
45 if (len > 7) {
46 int l = off;
47 int n = off + len - 1;
48 if (len > 40) { // Big arrays, pseudomedian of 9
49 int s = len/8;
50 l = med3(x, l, l+s, l+2*s);
51 m = med3(x, m-s, m, m+s);
52 n = med3(x, n-2*s, n-s, n);
53 }
54 m = med3(x, l, m, n); // Mid-size, med of 3
55 }
56 Comparable<Object> v = x[m];
57
58 // Establish Invariant: v* (<v)* (>v)* v*
59 int a = off, b = a, c = off + len - 1, d = c;
60 while(true) {
61 while (b <= c && x[b].compareTo(v) <= 0) {
62 if (x[b] == v)
63 swap(x, a++, b);
64 b++;
65 }
66 while (c >= b && x[c].compareTo(v) >= 0) {
67 if (x[c] == v)
68 swap(x, c, d--);
69 c--;
70 }
71 if (b > c)
72 break;
73 swap(x, b++, c--);
74 }
75
76 // Swap partition elements back to middle
77 int s, n = off + len;
78 s = Math.min(a-off, b-a ); vecswap(x, off, b-s, s);
79 s = Math.min(d-c, n-d-1); vecswap(x, b, n-s, s);
80
81 // Recursively sort non-partition-elements
82 if ((s = b-a) > 1)
83 sort1(x, off, s);
84 if ((s = d-c) > 1)
85 sort1(x, n-s, s);
86 }
87
88 /**
89 * Swaps x[a .. (a+n-1)] with x[b .. (b+n-1)].
90 */
91 private void vecswap(Object[] x, int a, int b, int n) {
92 for (int i=0; i<n; i++, a++, b++) {
93 swap(x, a, b);
94 }
95 }
96
97 /**
98 * Returns the index of the median of the three indexed integers.
99 */
100 private static int med3(Comparable<Object>[] x, int a, int b, int c) {
101 return (x[a].compareTo(x[b]) < 0 ?
102 (x[b].compareTo(x[c]) < 0 ? b : x[a].compareTo(x[c]) < 0 ? c : a) :
103 (x[b].compareTo(x[c]) > 0 ? b : x[a].compareTo(x[c]) > 0 ? c : a));
104 }
105
106
107 /**
108 * @return the reverse
109 */
110 public int[] getReverse() {
111 return reverse;
112 }
113
114 /**
115 * Swaps x[a] with x[b].
116 */
117 private void swap(Object[] x, int a, int b) {
118 Object t = x[a];
119 x[a] = x[b];
120 x[b] = t;
121 int z1 = reverse[a] != 0 ? reverse[a] : a+1;
122 int z2 = reverse[b] != 0 ? reverse[b] : b+1;
123 reverse[b] = z1;
124 reverse[a] = z2;
125 }
126 }