Breadth First Player

Author: jamesrcounts

src/main/java/org/teachingextensions/approvals/lite/Approvals.java

@@ -91,4 +91,7 @@ public static ApprovalNamer createApprovalNamer() {
     return new JUnitStackTraceNamer();
   }
 
+  public static void verify(Object o) throws Exception {
+    Approvals.verify(o + "");
+  }
 }

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

@@ -0,0 +1,39 @@
+package org.teachingextensions.logo;
+
+import java.util.*;
+
+/**
+ * A player who solves puzzles using breadth-first search.
+ */
+public class BreadthFirstPlayer {
+  private final Puzzle puzzle;
+  private final Set<PuzzleState>  visited  = new HashSet<>();
+  private final Queue<PuzzleState> frontier = new ArrayDeque<>();
+
+  public BreadthFirstPlayer(Puzzle puzzle) {
+
+    this.puzzle = puzzle;
+  }
+
+  public PuzzleState solve() {
+    PuzzleState state = new PuzzleState(this.puzzle);
+    do {
+      visited.add(state);
+      if (!state.isSolution()){
+        this.search(state);
+      }
+      state = frontier.remove();
+    } while (!state.isSolution());
+
+    return state;
+  }
+
+  private void search(PuzzleState state) {
+    List<PuzzleState> branches = state.getBranches();
+    for(PuzzleState b : branches){
+      if (!visited.contains(b)){
+        frontier.add(b);
+      }
+    }
+  }
+}

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

@@ -69,6 +69,14 @@ public List<PuzzleState> getBranches() {
     return branches;
   }
 
+  public Iterable<Direction> getHistory() {
+    return this.history;
+  }
+
+  public Puzzle getPuzzle() {
+    return this.puzzle;
+  }
+
   public enum Direction {
     Left(-1), Right(1), Up(-3), Down(3);
 

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

@@ -0,0 +1,34 @@
+package org.teachingextensions.logo;
+
+import org.junit.Test;
+import org.teachingextensions.approvals.lite.Approvals;
+import org.teachingextensions.approvals.lite.reporters.UseReporter;
+import org.teachingextensions.approvals.lite.reporters.macosx.BeyondCompareReporter;
+
+@UseReporter(BeyondCompareReporter.class)
+public class BreadthFirstPlayerTest {
+  /**
+   * Produces a puzzle solution
+   */
+  @Test
+  public void solve_puzzle() throws Exception {
+    int[] cells = {0, 1, 2, 3, 4, 5, 6, 8, 7};
+    Puzzle p = new Puzzle(cells);
+    BreadthFirstPlayer b = new BreadthFirstPlayer(p);
+    PuzzleState s = b.solve();
+    Approvals.verifyAll("Solve " + p, s.getHistory());
+  }
+
+  /**
+   * Solve longer puzzle
+   */
+  @Test
+  public void solve_longer_puzzle() throws Exception {
+    int[] cells = {0, 1, 2, 3, 4, 8, 5, 6, 7};
+    Puzzle p = new Puzzle(cells);
+    BreadthFirstPlayer b = new BreadthFirstPlayer(p);
+
+    PuzzleState s = b.solve();
+    Approvals.verifyAll("From " + p + " to " + s.getPuzzle(), s.getHistory());
+  }
+}

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

@@ -0,0 +1,16 @@
+From [0, 1, 2, 3, 4, 8, 5, 6, 7] to [0, 1, 2, 3, 4, 5, 6, 7, 8]
+
+
+{Down = 3}
+{Left = -1}
+{Left = -1}
+{Up = -3}
+{Right = 1}
+{Down = 3}
+{Right = 1}
+{Up = -3}
+{Left = -1}
+{Left = -1}
+{Down = 3}
+{Right = 1}
+{Right = 1}

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

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