src/main/java/com/cleverthis/interview/DumbBruteSolver.java

@@ -1,13 +1,15 @@
 package com.cleverthis.interview;
 
 import java.util.Arrays;
+import java.util.Collection;
 import java.util.Collections;
+import java.util.List;
 import java.util.stream.Stream;
 
 /**
- * Brute-forces padlock using lexicographically ordered permutation generation.
+ * Brute-forces padlock using lexicographically ordered permutation generation
  *
- * Permutation-generation algorithm documented at: https://en.wikipedia.org/wiki/Permutation#Generation_in_lexicographic_order
+ * Algorithm documented at: https://en.wikipedia.org/wiki/Permutation#Generation_in_lexicographic_order
  */
 public class DumbBruteSolver implements SolverInterface {
 
@@ -29,7 +31,7 @@ public class DumbBruteSolver implements SolverInterface {
             boolean isCorrect = checkPermutation(currentPermutation, padlockAdapter);
 
             if (!isCorrect) {
-                boolean nextPermutationExists = calculateNextPermutation(currentPermutation);
+                boolean nextPermutationExists = calculateNextPermutation(currentPermutation, numpadSize);
                 if(!nextPermutationExists) {
                     return;
                 }
@@ -58,11 +60,10 @@ public class DumbBruteSolver implements SolverInterface {
     /**
      * Calculates the next permutation in lexicographic order, based on the algorithm linked on wikipedia
      * @param currentPermutation The current permutation to run the algorithm on
+     * @param numpadSize The number of items in the set to be permuted
      * @return true if next permutation successfully generated, false if permutations have been exhausted
      */
-    protected boolean calculateNextPermutation(Integer[] currentPermutation) {
-        int numpadSize = currentPermutation.length;
-
+    protected boolean calculateNextPermutation(Integer[] currentPermutation, int numpadSize) {
         if(numpadSize < 2) { return false; }
 
         //Integer k, l;

src/main/java/com/cleverthis/interview/IntegerLevenshtein.java

@@ -3,7 +3,7 @@ package com.cleverthis.interview;
 import org.apache.commons.text.similarity.LevenshteinDistance;
 
 /**
- * Holds a single possible padlock passcode permutation in an integer array. This class
+ * A wrapper class that holds possible padlock passcode permutations in an integer array. This class
  * overloads the toString() method and is comparable, using its string value to calculate the levenshtein distance and
  * use those distance values for sorting into a data structure.
  */
@@ -50,7 +50,7 @@ public class IntegerLevenshtein implements Comparable<IntegerLevenshtein> {
     }
 
     /**
-     * Overridden compareTo method that compares the calculated levenshtein distance between two IntegerLevenshtein objects
+     * Overriden compareTo method that compares the calculated levenshtein distance between two IntegerLevenshtein objects
      * @param otherInteger the object to be compared.
      * @return The levenshtein distance between the two objects.
      */

src/main/java/com/cleverthis/interview/PadlockAdapter.java

@@ -1,7 +1,7 @@
 package com.cleverthis.interview;
 
 /**
- * This defines the contract that padlocks must conform to.
+ * This defines the interface that padlocks must conform to.
  * Concrete implementations will be adapted to this interface contract through concrete adapter classes.
  */
 public interface PadlockAdapter {

src/main/java/com/cleverthis/interview/SolverInterface.java

@@ -1,7 +1,7 @@
 package com.cleverthis.interview;
 
 /**
- * Defines the contract for padlock-cracking solver implementations
+ * Interface that defines the class signature for solver implementations
  */
 public interface SolverInterface {
 

src/main/java/com/cleverthis/interview/WriteAwareBruteSolver.java

@@ -1,9 +1,11 @@
 package com.cleverthis.interview;
 
+import java.util.Iterator;
 import java.util.TreeSet;
+import org.apache.commons.text.similarity.LevenshteinDistance;
 
 /**
- * A write-aware brute solver implementation that uses the levenshtein distance to sort passcode permutations
+ * This is a write-aware brute solver implementation that uses the levenshtein distance to sort passcode permutations
  * into a tree. Walking the tree in-order (Likely a depth-first traversal internally) results in a naive nearest-neighbor
  * optimization that generally performs well, but may perform poorly in some cases. Heuristic solutions exist that have
  * acceptable performance, and this is a more naive heuristic implementation.
@@ -15,7 +17,7 @@ import java.util.TreeSet;
  * A more advanced solution (based on Christofides, or another TSP heuristic) may result in more performance gains, but
  * the performance of this nearest-neighbor solution is adequate for the keypad sizes under test. A keypad size of 9
  * results in a graph of vertex-count 9!. It's unlikely performance gains from a more intelligent TSP solver would
- * offset the performance cost of building a graph and solving for an optimal tour.
+ * offset the performance cost of building a graph and optimizing traversal.
  */
 public class WriteAwareBruteSolver extends DumbBruteSolver {
 
@@ -66,8 +68,10 @@ public class WriteAwareBruteSolver extends DumbBruteSolver {
      * @param size The number of keys on the numpad
      */
     protected void createOrderedTree(int size) {
-        this.numpadSize = size;
-        orderedTree.clear();
+        if(this.numpadSize != size) {
+            this.numpadSize = size;
+            orderedTree.clear();
+        }
 
         Integer[] currentPermutation = new Integer[numpadSize];
         for(int i = 0; i < numpadSize; i++) {
@@ -80,7 +84,7 @@ public class WriteAwareBruteSolver extends DumbBruteSolver {
             IntegerLevenshtein levenshteinPermutation = new IntegerLevenshtein(numpadSize);
             levenshteinPermutation.setIntegerData(currentPermutation);
             orderedTree.add(levenshteinPermutation);
-            morePermutationsExist = this.calculateNextPermutation(currentPermutation);
+            morePermutationsExist = this.calculateNextPermutation(currentPermutation, numpadSize);
         } while(morePermutationsExist);
     }
 }

src/test/java/com/cleverthis/interview/DumbBruteSolverTest.java

@@ -43,7 +43,7 @@ public class DumbBruteSolverTest extends SolutionTestBase {
         Integer[] permutation = new Integer[] {1, 2, 3, 4};
         Integer[] correctPermutation = new Integer[] {1, 2, 4, 3};
 
-        dumbSolver.calculateNextPermutation(permutation);
+        dumbSolver.calculateNextPermutation(permutation, 4);
 
         assertArrayEquals(permutation, correctPermutation);
     }
@@ -59,7 +59,7 @@ public class DumbBruteSolverTest extends SolutionTestBase {
         Integer[] correctPermutation = new Integer[] {1, 3, 2, 4};
 
         for(int i = 0; i < 2; i++) {
-            dumbSolver.calculateNextPermutation(permutation);
+            dumbSolver.calculateNextPermutation(permutation, 4);
         }
 
         assertArrayEquals(permutation, correctPermutation);
@@ -76,7 +76,7 @@ public class DumbBruteSolverTest extends SolutionTestBase {
         Integer[] correctPermutation = new Integer[] {4, 3, 2, 1};
 
         for(int i = 0; i < 23; i++) {
-            dumbSolver.calculateNextPermutation(permutation);
+            dumbSolver.calculateNextPermutation(permutation, 4);
         }
 
         assertArrayEquals(permutation, correctPermutation);
@@ -93,10 +93,10 @@ public class DumbBruteSolverTest extends SolutionTestBase {
         Integer[] permutation = new Integer[] {1, 2, 3, 4};
 
         for(int i = 0; i < 23; i++) {
-            assertTrue(dumbSolver.calculateNextPermutation(permutation));
+            assertTrue(dumbSolver.calculateNextPermutation(permutation, 4));
         }
 
-        assertFalse(dumbSolver.calculateNextPermutation(permutation));
+        assertFalse(dumbSolver.calculateNextPermutation(permutation, 4));
 
     }
 }

src/test/java/com/cleverthis/interview/PerformanceAnalyze.java

@@ -1,5 +1,7 @@
 package com.cleverthis.interview;
 
+import com.cleverthis.interview.padlock.PadlockImpl;
+
 /**
  * Performance test but not mean to run in unit test.
  */

src/test/java/com/cleverthis/interview/SolutionTestBase.java

@@ -1,5 +1,6 @@
 package com.cleverthis.interview;
 
+import com.cleverthis.interview.padlock.PadlockImpl;
 import org.junit.jupiter.api.Test;
 
 import static org.junit.jupiter.api.Assertions.assertTrue;