Fixed formatting and build issues for Sudoku Solver

Author: khalidx3

src/main/java/com/thealgorithms/backtracking/SudokuSolver.java

@@ -1,61 +1,58 @@
 package main.java.com.thealgorithms.backtracking;
 
 public class SudokuSolver {
-      public static boolean sudokuSolver(int sudoku[][], int row, int col) {
-            // base case
+
+      public static boolean sudokuSolver(int[][] sudoku, int row, int col) {
             if (row == 9) {
-                  return true;
+                  return true; // base case: reached the end
             }
-            // recursion
-            int nextRow = row, nextCol = col + 1;
-            if (col + 1 == 9) {
+
+            int nextRow = row;
+            int nextCol = col + 1;
+            if (nextCol == 9) {
                   nextRow = row + 1;
                   nextCol = 0;
             }
+
             if (sudoku[row][col] != 0) {
                   return sudokuSolver(sudoku, nextRow, nextCol);
             }
-            for (int digit = 1; digit <= 9; digit++) {
-                  if (isSafe(sudoku, row, col, digit)) {
-                        sudoku[row][col] = digit;
 
+            for (int num = 1; num <= 9; num++) {
+                  if (isSafe(sudoku, row, col, num)) {
+                        sudoku[row][col] = num;
                         if (sudokuSolver(sudoku, nextRow, nextCol)) {
                               return true;
                         }
-                        sudoku[row][col] = 0;
+                        sudoku[row][col] = 0; // backtrack
                   }
             }
-
             return false;
       }
 
-      public static boolean isSafe(int sudoku[][], int row, int col, int digit) {
-            // col
-            for (int i = 0; i <= 8; i++) {
-                  if (sudoku[i][col] == digit) {
-                        return false;
-                  }
-            }
-            // row
-            for (int j = 0; j <= 8; j++) {
-                  if (sudoku[row][j] == digit) {
+      private static boolean isSafe(int[][] sudoku, int row, int col, int num) {
+            // Check row and column
+            for (int i = 0; i < 9; i++) {
+                  if (sudoku[row][i] == num || sudoku[i][col] == num) {
                         return false;
                   }
             }
-            // grid
-            int sr = (row / 3) * 3;
-            int sc = (col / 3) * 3;
-            for (int i = sr; i < sr + 3; i++) {
-                  for (int j = sc; i < sr + 3; i++) {
-                        if (sudoku[i][j] == digit) {
+
+            // Check 3x3 subgrid
+            int startRow = row - row % 3;
+            int startCol = col - col % 3;
+            for (int i = startRow; i < startRow + 3; i++) {
+                  for (int j = startCol; j < startCol + 3; j++) {
+                        if (sudoku[i][j] == num) {
                               return false;
                         }
                   }
             }
+
             return true;
       }
 
-      public static void print(int sudoku[][]) {
+      private static void printSudoku(int[][] sudoku) {
             for (int i = 0; i < 9; i++) {
                   for (int j = 0; j < 9; j++) {
                         System.out.print(sudoku[i][j] + " ");
@@ -65,21 +62,23 @@ public static void print(int sudoku[][]) {
       }
 
       public static void main(String[] args) {
-            int sudoku[][] = { { 3, 0, 6, 5, 0, 8, 4, 0, 0 },
-                        { 5, 2, 0, 0, 0, 0, 0, 0, 0 },
-                        { 0, 8, 7, 0, 0, 0, 0, 3, 1 },
-                        { 0, 0, 3, 0, 1, 0, 0, 8, 0 },
-                        { 9, 0, 0, 8, 6, 3, 0, 0, 5 },
-                        { 0, 5, 0, 0, 9, 0, 6, 0, 0 },
-                        { 1, 3, 0, 0, 0, 0, 2, 5, 0 },
-                        { 0, 0, 0, 0, 0, 0, 0, 7, 4 },
-                        { 0, 0, 5, 2, 0, 6, 3, 0, 0 } };
-            if (sudokuSolver(sudoku, 0, 0)) {
+            int[][] sudoku = {
+                        { 5, 3, 0, 0, 7, 0, 0, 0, 0 },
+                        { 6, 0, 0, 1, 9, 5, 0, 0, 0 },
+                        { 0, 9, 8, 0, 0, 0, 0, 6, 0 },
+                        { 8, 0, 0, 0, 6, 0, 0, 0, 3 },
+                        { 4, 0, 0, 8, 0, 3, 0, 0, 1 },
+                        { 7, 0, 0, 0, 2, 0, 0, 0, 6 },
+                        { 0, 6, 0, 0, 0, 0, 2, 8, 0 },
+                        { 0, 0, 0, 4, 1, 9, 0, 0, 5 },
+                        { 0, 0, 0, 0, 8, 0, 0, 7, 9 }
+            };
 
-                  print(sudoku);
+            if (sudokuSolver(sudoku, 0, 0)) {
+                  System.out.println("Sudoku Solved:");
+                  printSudoku(sudoku);
             } else {
-                  System.out.println("not valid");
+                  System.out.println("No solution exists.");
             }
       }
-
 }