Change project structure to a Maven Java project + Refactor (#2816)

src/main/java/com/thealgorithms/others/Sudoku.java

@@ -0,0 +1,134 @@
+package com.thealgorithms.others;
+
+class Sudoku {
+
+    public static boolean isSafe(int[][] board,
+            int row, int col,
+            int num) {
+        // Row has the unique (row-clash)
+        for (int d = 0; d < board.length; d++) {
+
+            // Check if the number we are trying to
+            // place is already present in
+            // that row, return false;
+            if (board[row][d] == num) {
+                return false;
+            }
+        }
+
+        // Column has the unique numbers (column-clash)
+        for (int r = 0; r < board.length; r++) {
+
+            // Check if the number
+            // we are trying to
+            // place is already present in
+            // that column, return false;
+            if (board[r][col] == num) {
+                return false;
+            }
+        }
+
+        // Corresponding square has
+        // unique number (box-clash)
+        int sqrt = (int) Math.sqrt(board.length);
+        int boxRowStart = row - row % sqrt;
+        int boxColStart = col - col % sqrt;
+
+        for (int r = boxRowStart;
+                r < boxRowStart + sqrt; r++) {
+            for (int d = boxColStart;
+                    d < boxColStart + sqrt; d++) {
+                if (board[r][d] == num) {
+                    return false;
+                }
+            }
+        }
+
+        // if there is no clash, it's safe
+        return true;
+    }
+
+    public static boolean solveSudoku(
+            int[][] board, int n) {
+        int row = -1;
+        int col = -1;
+        boolean isEmpty = true;
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < n; j++) {
+                if (board[i][j] == 0) {
+                    row = i;
+                    col = j;
+
+                    // We still have some remaining
+                    // missing values in Sudoku
+                    isEmpty = false;
+                    break;
+                }
+            }
+            if (!isEmpty) {
+                break;
+            }
+        }
+
+        // No empty space left
+        if (isEmpty) {
+            return true;
+        }
+
+        // Else for each-row backtrack
+        for (int num = 1; num <= n; num++) {
+            if (isSafe(board, row, col, num)) {
+                board[row][col] = num;
+                if (solveSudoku(board, n)) {
+                    // print(board, n);
+                    return true;
+                } else {
+                    // replace it
+                    board[row][col] = 0;
+                }
+            }
+        }
+        return false;
+    }
+
+    public static void print(
+            int[][] board, int N) {
+
+        // We got the answer, just print it
+        for (int r = 0; r < N; r++) {
+            for (int d = 0; d < N; d++) {
+                System.out.print(board[r][d]);
+                System.out.print(" ");
+            }
+            System.out.print("\n");
+
+            if ((r + 1) % (int) Math.sqrt(N) == 0) {
+                System.out.print("");
+            }
+        }
+    }
+
+    // Driver Code
+    public static void main(String args[]) {
+
+        int[][] board = new int[][]{
+            {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}
+        };
+        int N = board.length;
+
+        if (solveSudoku(board, N)) {
+            // print solution
+            print(board, N);
+        } else {
+            System.out.println("No solution");
+        }
+    }
+}