package com.walker.etaa.util;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.Random;
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public class AlgorithmUtils {
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private static final Logger logger = LoggerFactory.getLogger(AlgorithmUtils.class);
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private static final Random random = new Random();
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/**
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* 返回给定数据的 HashCode 值集合。
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* @param prefix 字符串前缀，如：math
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* @param indexList 数据记录索引集合，如：[1,3,5,7,...]
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* @return
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* @date 2023-03-08
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*/
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public static final List<Integer> getHashCode(String prefix, int[] indexList){
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if(indexList == null || indexList.length == 0){
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return null;
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}
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List<Integer> resultList = new ArrayList<>(indexList.length + 8);
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String s = null;
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for(int i=0; i<indexList.length; i++){
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s = prefix + indexList[i];
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resultList.add(s.hashCode());
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}
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return resultList;
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}
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/**
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* 返回给定范围可用的（随机）数据索引编号集合，如：
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* <pre>
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* [1,8,5,12,33,...]
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* </pre>
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* @param existTotal
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* @param requiredTotal
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* @return
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*/
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public static final int[] getRandomIndexArray(int existTotal, int requiredTotal){
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int span = existTotal / requiredTotal;
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int offset = 1;
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if(span > 1){
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offset = Math.abs(random.nextInt(span));
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} else {
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offset = Math.abs(random.nextInt(requiredTotal-1));
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}
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if(offset >= existTotal || offset <= 0){
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offset = 1;
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}
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int count = 0;
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List<Integer> data = new ArrayList<>();
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while (count < requiredTotal){
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if(offset >= existTotal || offset <= 0){
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offset = Math.abs(random.nextInt(requiredTotal-1));
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// logger.debug("------> offset = {}", offset);
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}
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if(!data.contains(offset)){
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// logger.debug(".......... offset = {}", offset);
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data.add(offset);
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// offset = random.nextInt(requiredTotal-1) + span;
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offset = Math.abs(random.nextInt(existTotal-1)) + span;
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count ++;
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logger.debug("count = {}, offset = {}", count, offset);
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} else {
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// 已有重复了，
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// offset = count + 1;
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offset = Math.abs(random.nextInt(existTotal-1));
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logger.debug("重复了，offset = {}", offset);
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}
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}
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if(data.size() > 0){
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int[] resultList = new int[data.size()];
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for(int i=0; i<data.size(); i++){
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resultList[i] = data.get(i);
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}
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return resultList;
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}
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return null;
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}
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/**
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* 返回给定范围可用的（平均分布）数据索引编号集合，如：
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* <pre>
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* [1,3,5,7,9,...]
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* </pre>
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* @param existTotal
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* @param requiredTotal
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* @return
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*/
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public static final int[] getAverageIndexArray(int existTotal, int requiredTotal){
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int[] result = new int[requiredTotal];
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int span = existTotal / requiredTotal;
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int offset = Math.abs(random.nextInt(10));
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logger.debug("offset = " + offset);
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if(span == 1){
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for(int i=0; i<requiredTotal; i++){
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// System.out.println("get " + (i+1));
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result[i] = i+1;
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}
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} else if(span > 1){
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int current = offset;
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if(current == 0){
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current = 1;
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}
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int last = AlgorithmUtils.getAverageLastIndex(current, span, requiredTotal);
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while(last > existTotal){
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logger.debug("最后元素超过了'existTotal'，last = " + last);
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if(span > 1){
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span --;
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} else if(offset > 1){
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offset --;
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} else {
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logger.warn("已经无法降低抽取间隔了，退出循环");
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break;
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}
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last = AlgorithmUtils.getAverageLastIndex(current, span, requiredTotal);
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}
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for(int i=0; i<requiredTotal; i++){
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if(i > 0){
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current += span;
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}
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// System.out.println("get " + (current));
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result[i] = current;
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}
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}
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return result;
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}
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/**
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* 返回平均分布方式抽取时，计算最后元素的索引值（计数值，是否超过题库最大值）
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* @param first 第一个元素索引，从
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* @param span
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* @param requiredTotal
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* @return
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*/
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public static final int getAverageLastIndex(int first, int span, int requiredTotal){
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int current = first;
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for(int i=0; i<requiredTotal; i++){
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if(i > 0){
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current += span;
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}
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// System.out.println("get " + (current));
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}
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return current;
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}
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}
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