[JAVA-22175] Sudoku for-loop to avoid side effects (eugenp#17183)

SmartyAnsh · Aug 5, 2024 · 4dabff8 · 4dabff8
1 parent 42c1ba7
commit 4dabff8
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Showing 3 changed files with 42 additions and 7 deletions.
diff --git a/...s-miscellaneous-2/src/main/java/com/baeldung/algorithms/sudoku/BacktrackingAlgorithm.java b/...s-miscellaneous-2/src/main/java/com/baeldung/algorithms/sudoku/BacktrackingAlgorithm.java
@@ -12,7 +12,7 @@ public class BacktrackingAlgorithm {
     private static final int MIN_VALUE = 1;
     private static final int MAX_VALUE = 9;
 
-    private static int[][] board = {
+    private static final int[][] board = {
       {8, 0, 0, 0, 0, 0, 0, 0, 0},
       {0, 0, 3, 6, 0, 0, 0, 0, 0},
       {0, 7, 0, 0, 9, 0, 2, 0, 0},
@@ -39,7 +39,7 @@ private void printBoard() {
         }
     }
 
-    private boolean solve(int[][] board) {
+    public boolean solve(int[][] board) {
         for (int row = BOARD_START_INDEX; row < BOARD_SIZE; row++) {
             for (int column = BOARD_START_INDEX; column < BOARD_SIZE; column++) {
                 if (board[row][column] == NO_VALUE) {
@@ -81,14 +81,22 @@ private boolean subsectionConstraint(int[][] board, int row, int column) {
 
     private boolean columnConstraint(int[][] board, int column) {
         boolean[] constraint = new boolean[BOARD_SIZE];
-        return IntStream.range(BOARD_START_INDEX, BOARD_SIZE)
-          .allMatch(row -> checkConstraint(board, row, constraint, column));
+        for (int row = BOARD_START_INDEX; row < BOARD_SIZE; row++) {
+            if (!checkConstraint(board, row, constraint, column)) {
+                return false;
+            }
+        }
+        return true;
     }
 
     private boolean rowConstraint(int[][] board, int row) {
         boolean[] constraint = new boolean[BOARD_SIZE];
-        return IntStream.range(BOARD_START_INDEX, BOARD_SIZE)
-          .allMatch(column -> checkConstraint(board, row, constraint, column));
+        for (int column = BOARD_START_INDEX; column < BOARD_SIZE; column++) {
+            if (!checkConstraint(board, row, constraint, column)) {
+                return false;
+            }
+        }
+        return true;
     }
 
     private boolean checkConstraint(int[][] board, int row, boolean[] constraint, int column) {

diff --git a/...s-miscellaneous-2/src/main/java/com/baeldung/algorithms/sudoku/DancingLinksAlgorithm.java b/...s-miscellaneous-2/src/main/java/com/baeldung/algorithms/sudoku/DancingLinksAlgorithm.java
@@ -11,7 +11,7 @@ public class DancingLinksAlgorithm {
     private static final int MAX_VALUE = 9;
     private static final int COVER_START_INDEX = 1;
 
-    private static int[][] board = {
+    private static final int[][] board = {
       {8, 0, 0, 0, 0, 0, 0, 0, 0},
       {0, 0, 3, 6, 0, 0, 0, 0, 0},
       {0, 7, 0, 0, 9, 0, 2, 0, 0},

diff --git a/...llaneous-2/src/test/java/com/baeldung/algorithms/sudoku/BacktrackingAlgoritmUnitTest.java b/...llaneous-2/src/test/java/com/baeldung/algorithms/sudoku/BacktrackingAlgoritmUnitTest.java
@@ -0,0 +1,27 @@
+package com.baeldung.algorithms.sudoku;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class BacktrackingAlgoritmUnitTest {
+
+    private static final int[][] board = {
+        {8, 0, 0, 0, 0, 0, 0, 0, 0},
+        {0, 0, 3, 6, 0, 0, 0, 0, 0},
+        {0, 7, 0, 0, 9, 0, 2, 0, 0},
+        {0, 5, 0, 0, 0, 7, 0, 0, 0},
+        {0, 0, 0, 0, 4, 5, 7, 0, 0},
+        {0, 0, 0, 1, 0, 0, 0, 3, 0},
+        {0, 0, 1, 0, 0, 0, 0, 6, 8},
+        {0, 0, 8, 5, 0, 0, 0, 1, 0},
+        {0, 9, 0, 0, 0, 0, 4, 0, 0}
+    };
+
+    @Test
+    public void testSudokuBacktrackingAlgorithm() {
+        BacktrackingAlgorithm solver = new BacktrackingAlgorithm();
+        solver.solve(board);
+        Assert.assertArrayEquals(board[0], new int[] {8,1,2,7,5,3,6,4,9});
+    }
+
+}