139 lines
3.9 KiB
Java
139 lines
3.9 KiB
Java
package Presenter.Algorithms;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.List;
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/**
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* Implementierung verschiedener Algorithmen zur Berechnung von Ausgleichsgeraden.
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*
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* @Author: Armin Wolf
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* @Email: a_wolf28@uni-muenster.de
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* @Date: 18.06.2017.
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*/
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public class InversionCounter {
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private HashMap<Integer, Integer> dictionaryTO;
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private HashMap<Integer, Integer> dictionaryBACK;
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private ArrayList<Integer> substituted;
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private ArrayList<Pair> inversions;
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private class Pair{
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private Integer p1;
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private Integer p2;
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public Pair(Integer p1, Integer p2) {
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this.p1 = p1;
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this.p2 = p2;
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}
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public Integer getP1() {
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return p1;
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}
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public void setP1(Integer p1) {
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this.p1 = p1;
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}
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public Integer getP2() {
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return p2;
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}
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public void setP2(Integer p2) {
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this.p2 = p2;
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}
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}
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public int run(List<Integer> a, List<Integer> b){
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dictionaryTO = new HashMap<>();
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dictionaryBACK = new HashMap<>();
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substituted = new ArrayList<>();
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inversions = new ArrayList<>();
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ArrayList<Integer> temp = new ArrayList<>();
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temp.addAll(a);
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for (int i=0;i<a.size();i++){
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dictionaryTO.put(a.get(i), i+1 );
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dictionaryBACK.put(i+1 , a.get(i));
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}
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for (int j=0;j<b.size();j++){
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substituted.add(dictionaryTO.get(b.get(j)));
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}
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int ret = countInversions(substituted, 0, substituted.size()-1, temp);
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getInversionPairs();
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dictionaryTO = null;
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substituted = null;
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inversions = null;
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return ret;
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}
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/**
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* Angepasster Merge-Sort Algorithmus.
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* Die Funktion bekommt neben den standard Parametern zusätzlich eine Liste mit Elementen
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* die als Groundtruth dienen.
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* @param a Eingabefeld mit den Elementen die überprüft werden sollen.
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* @param start Startpunkt des Eingabefeldes.
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* @param end Endpunkt des Eingabefeldes.
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* @param aux Groundtruth Ordnung um die Anzahl der Inversionen zu bestimmen.
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* @return Anzahl der inversionen zwischen a und aux.
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*/
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public int countInversions(List<Integer> a, int start, int end, List<Integer> aux) {
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if (start >= end) {
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return 0;
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}
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int invCount = 0;
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int mid = start + (end - start) / 2;
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int invCountLeft = countInversions(a, start, mid, aux); // divide and conquer
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int invCountRight = countInversions(a, mid + 1, end, aux); // divide and conquer
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invCount += (invCountLeft + invCountRight);
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for (int i = start; i <= end; i++) {
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aux.set(i, a.get(i));
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}
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int left = start;
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int right = mid + 1;
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int index = start;
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while (left <= mid && right <= end) {
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if (aux.get(left) < aux.get(right)) {
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a.set(index++, aux.get(left++));
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} else {
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for (int i=left; i<=mid;i++){
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// System.out.println(aux.get(i)+" -- "+ aux.get(right));
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inversions.add(new Pair(aux.get(i), aux.get(right)));
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}
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a.set(index++, aux.get(right++));
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invCount += mid - left + 1; // number of inversions for aux[right]
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}
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}
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while (left <= mid) {
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a.set(index++, aux.get(left++));
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}
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// no need to copy over remaining aux[right++] because they are already inside a
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return invCount;
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}
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public void getInversionPairs(){
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ArrayList<Pair> result = new ArrayList<>();
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for (int i=0;i<inversions.size();i++){
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result.add(new Pair(dictionaryBACK.get(inversions.get(i).getP1()), dictionaryBACK.get(inversions.get(i).getP2())));
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}
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//for (Pair p : result){
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// System.out.println(p.getP1() + " <==> " + p.getP2());
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//}
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}
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}
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