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HSQLDB example source code file (ArrayCounter.java)
The HSQLDB ArrayCounter.java source code/* Copyright (c) 2001-2008, The HSQL Development Group * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * * Redistributions of source code must retain the above copyright notice, this * list of conditions and the following disclaimer. * * Redistributions in binary form must reproduce the above copyright notice, * this list of conditions and the following disclaimer in the documentation * and/or other materials provided with the distribution. * * Neither the name of the HSQL Development Group nor the names of its * contributors may be used to endorse or promote products derived from this * software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL HSQL DEVELOPMENT GROUP, HSQLDB.ORG, * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ package org.hsqldb.lib; /** * Collection of routines for counting the distribution of the values * in an int[] array. * * @author fredt@users * @version 1.7.2 * @since 1.7.2 */ public class ArrayCounter { /** * Returns an int[] array of length segments containing the distribution * count of the elements in unsorted int[] array with values between min * and max (range). Values outside the min-max range are ignored<p> * * A usage example is determining the count of people of each age group * in a large int[] array containing the age of each person. Called with * (array, 16,0,79), it will return an int[16] with the first element * the count of people aged 0-4, the second element the count of those * aged 5-9, and so on. People above the age of 79 are excluded. If the * range is not a multiple of segments, the last segment will be cover a * smaller sub-range than the rest. * */ public static int[] countSegments(int[] array, int elements, int segments, int start, int limit) { int[] counts = new int[segments]; long interval = calcInterval(segments, start, limit); int index = 0; int element = 0; if (interval <= 0) { return counts; } for (int i = 0; i < elements; i++) { element = array[i]; if (element < start || element >= limit) { continue; } index = (int) ((element - start) / interval); counts[index]++; } return counts; } /** * With an unsorted int[] array and with target a positive integer in the * range (1,array.length), finds the value in the range (start,limit) of the * largest element (rank) where the count of all smaller elements in that * range is less than or equals target. Parameter margin indicates the * margin of error in target<p> * * In statistics, this can be used to calculate a median or quadrile value. * A usage example applied to an array of age values is to determine * the maximum age of a given number of people. With the example array * given in countSegments, rank(array, c, 6000, 18, 65, 0) will return an age * value between 18-64 (inclusive) and the count of all people aged between * 18 and the returned value(exclusive) will be less than or equal 6000. * */ public static int rank(int[] array, int elements, int target, int start, int limit, int margin) { final int segments = 256; int elementCount = 0; int currentLimit = limit; for (;;) { long interval = calcInterval(segments, start, currentLimit); int[] counts = countSegments(array, elements, segments, start, currentLimit); for (int i = 0; i < counts.length; i++) { if (elementCount + counts[i] < target) { elementCount += counts[i]; start += interval; } else { break; } } if (elementCount + margin >= target) { return start; } if (interval <= 1) { return start; } currentLimit = start + interval < limit ? (int) (start + interval) : limit; } } /** * Helper method to calculate the span of the sub-interval. Simply returns * the cieling of ((limit - start) / segments) and accounts for invalid * start and limit combinations. */ static long calcInterval(int segments, int start, int limit) { long range = limit - start; if (range < 0) { return 0; } int partSegment = (range % segments) == 0 ? 0 : 1; return (range / segments) + partSegment; } } Other HSQLDB examples (source code examples)Here is a short list of links related to this HSQLDB ArrayCounter.java source code file: |
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