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A Star Player
1 parent 3d7912c commit bd1693f

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+301
-25
lines changed

‎src/main/java/org/teachingextensions/logo/AStarEstimator.java‎

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package org.teachingextensions.logo;
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import java.util.Comparator;
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public class AStarEstimator implements Comparator<PuzzleState> {
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@Override
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public int compare(PuzzleState left, PuzzleState right) {
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return costOf(left) - costOf(right);
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}
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private int costOf(PuzzleState state) {
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return state.getActualCost() + state.getEstimatedCost();
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}
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}

‎src/main/java/org/teachingextensions/logo/AStarPlayer.java‎

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package org.teachingextensions.logo;
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import java.util.PriorityQueue;
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/**
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* A player who solves puzzles using the A* strategy will not only take into account the known cost of a reaching
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* a puzzle state, but also estimates the remaining cost to the goal.
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*/
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public class AStarPlayer extends PuzzlePlayer {
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public AStarPlayer(Puzzle puzzle) {
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super(puzzle, new PriorityQueue<>(1, new AStarEstimator()));
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}
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}

‎src/main/java/org/teachingextensions/logo/Puzzle.java‎

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package org.teachingextensions.logo;
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import java.awt.*;
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import java.util.Arrays;
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/**
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* @see <a href="http://en.wikipedia.org/wiki/15_puzzle">Wikipedia</a>
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*/
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public class Puzzle {
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private static final int[] solution = {0, 1, 2, 3, 4, 5, 6, 7, 8};
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private static final int blank = 8;
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private static final int blank = 8;
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private final int[] cells;
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public Puzzle(int[] cells) {
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this.cells = cells;
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}
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/**
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* Gives the position of the cell as it would appear on a 3x3 board.
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*
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* @param cell
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* The cell to get the position for.
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* @return The position of the cell.
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*/
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public static Point getPosition(int cell) {
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return new Point(cell % 3, cell / 3);
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}
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/**
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* Calculate the <a href="http://en.wikipedia.org/wiki/Taxicab_geometry">Manhattan Distance</a> between two positions.
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*
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* @param start
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* The starting position.
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* @param end
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* The ending position.
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* @return The distance between the two positions.
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*/
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public static int getDistance(Point start, Point end) {
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return Math.abs(start.x - end.x) + Math.abs(start.y - end.y);
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}
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/**
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* Calculate the <a href="http://en.wikipedia.org/wiki/Taxicab_geometry">Manhattan Distance</a> between two cells by first converting them to positions.
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*
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* @param start
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* The starting cell
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* @param end
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* The ending cell
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* @return The distance between the cells.
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*/
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public static int getDistance(int start, int end) {
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return getDistance(getPosition(start), getPosition(end));
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}
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@Override
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public int hashCode() {
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return Arrays.hashCode(cells);
@@ -38,12 +75,7 @@ public String toString() {
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}
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public boolean isSolved() {
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for (int i = 0; i < solution.length; i++) {
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if (solution[i] != cells[i]) {
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return false;
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}
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}
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return true;
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return getDistanceToGoal() == 0;
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}
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public int getBlankIndex() {
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copy[target] = 8;
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return new Puzzle(copy);
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}
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/**
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* Calculate the distance between the goal by summing the distance between each cell and its goal.
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*
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* @return The distance to the goal.
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*/
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public int getDistanceToGoal() {
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int distance = 0;
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for (int i = 0; i < cells.length; i++) {
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distance += getDistance(i, cells[i]);
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}
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return distance;
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}
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}

‎src/main/java/org/teachingextensions/logo/PuzzleState.java‎

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* Represents a node in the puzzle-solving graph. Keeps track of the current puzzle arrangement and the actions
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* required to arrive at the current arrangement from the starting arrangement.
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*/
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public class PuzzleState implements Comparator<PuzzleState> , Comparable<PuzzleState>{
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public class PuzzleState implements Comparator<PuzzleState>, Comparable<PuzzleState> {
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private final Puzzle puzzle;
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private final Stack<Direction> history;
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return puzzle.isSolved();
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}
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@Override
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public String toString() {
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StringBuilder b = new StringBuilder();
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if (!history.isEmpty()) {
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b.append(history.peek());
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b.append(" to ");
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}
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b.append(puzzle);
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return b.toString();
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}
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public List<PuzzleState> getBranches() {
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List<PuzzleState> branches = new ArrayList<>(4);
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int blank = puzzle.getBlankIndex();
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}
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@Override
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public int compareTo( PuzzleState o) {
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public int compareTo(PuzzleState o) {
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return compare(this, o);
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}
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@Override
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public int hashCode() {
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return puzzle.hashCode();
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}
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@Override
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public boolean equals(Object o) {
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if (this == o) return true;
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}
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@Override
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public int hashCode() {
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return puzzle.hashCode();
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public String toString() {
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StringBuilder b = new StringBuilder();
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if (!history.isEmpty()) {
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b.append(history.peek());
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b.append(" to ");
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}
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b.append(puzzle);
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return b.toString();
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}
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public int getEstimatedCost() {
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return puzzle.getDistanceToGoal();
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}
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public enum Direction {

‎src/test/java/org/teachingextensions/logo/AStarPlayerTest.java‎

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package org.teachingextensions.logo;
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import org.junit.Test;
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import org.teachingextensions.approvals.lite.Approvals;
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import org.teachingextensions.approvals.lite.reporters.UseReporter;
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import org.teachingextensions.approvals.lite.reporters.macosx.BeyondCompareReporter;
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@UseReporter(BeyondCompareReporter.class)
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public class AStarPlayerTest extends PuzzlePlayerTest {
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@Override
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protected PuzzlePlayer getPlayer(Puzzle puzzle) {
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return new AStarPlayer(puzzle);
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}
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/**
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* Produces a puzzle solution
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*/
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@Test
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public void solve_puzzle() throws Exception {
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verifySolution();
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}
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/**
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* Solve longer puzzle
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*/
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@Test
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public void solve_longer_puzzle() throws Exception {
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verifyLongSolution();
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}
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/**
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* Solve jumbo puzzle
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*/
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@Test
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public void solve_jumbo_puzzle() throws Exception {
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int[] cells = {8, 0, 1, 2, 3, 4, 5, 6, 7};
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Puzzle p = new Puzzle(cells);
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PuzzlePlayer b = getPlayer(p);
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PuzzleState s = b.solve();
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Approvals.verifyAll("From " + p + " to " + s.getPuzzle(), s.getHistory());
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}
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}

‎src/test/java/org/teachingextensions/logo/AStarPlayerTest.solve_jumbo_puzzle.approved.txt‎

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From [8, 0, 1, 2, 3, 4, 5, 6, 7] to [0, 1, 2, 3, 4, 5, 6, 7, 8]
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{Right = 1}
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{Down = 3}
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{Left = -1}
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{Down = 3}
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{Right = 1}
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{Right = 1}
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{Up = -3}
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{Left = -1}
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{Left = -1}
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{Down = 3}
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{Right = 1}
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{Up = -3}
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{Up = -3}
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{Right = 1}
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{Down = 3}
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{Down = 3}
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{Left = -1}
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{Left = -1}
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{Up = -3}
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{Right = 1}
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{Right = 1}
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{Down = 3}

‎src/test/java/org/teachingextensions/logo/AStarPlayerTest.solve_longer_puzzle.approved.txt‎

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From [0, 1, 2, 3, 4, 8, 5, 6, 7] to [0, 1, 2, 3, 4, 5, 6, 7, 8]
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{Down = 3}
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{Left = -1}
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{Left = -1}
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{Up = -3}
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{Right = 1}
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{Down = 3}
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{Right = 1}
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{Up = -3}
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{Left = -1}
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{Left = -1}
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{Down = 3}
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{Right = 1}
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{Right = 1}

‎src/test/java/org/teachingextensions/logo/AStarPlayerTest.solve_puzzle.approved.txt‎

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Solve [0, 1, 2, 3, 4, 5, 6, 8, 7]
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{Right = 1}

src/main/java/org/teachingextensions/logo/PuzzlePlayerTest.java renamed to src/test/java/org/teachingextensions/logo/PuzzlePlayerTest.java

File renamed without changes.

‎src/test/java/org/teachingextensions/logo/PuzzleStateTest.java‎

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assertNotEquals(a, b);
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}
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/**
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* The estimated cost is zero when puzzle is solved.
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*/
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@Test
115+
public void estimated_cost_is_zero_when_solved() {
116+
PuzzleState s = new PuzzleState(getSolvedPuzzle());
117+
assertEquals(0, s.getEstimatedCost());
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}
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/**
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* The estimated cost is the distance to goal when the puzzle is not solved.
122+
*/
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@Test
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public void estimated_cost_is_goal_distance_when_unsolved() {
125+
Puzzle p = getPuzzle(7);
126+
p = p.swapBlank(4);
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PuzzleState s = new PuzzleState(p);
128+
assertEquals(p.getDistanceToGoal(), s.getEstimatedCost());
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}
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/**
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* Is equal to another state when the puzzles are the same
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*/

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