added

Author: anujvaghani0

src/Backtracking/sudokuSolver.java

@@ -60,6 +60,7 @@ public static boolean solve(int[][] board) {
         }
 
 //        backtrack
+
         for (int number = 0; number <= 9; number++) {
             if (isSafe(board, row, col, number)) {
                 board[row][col] = number;

src/Backtracking/sudokuSolverUsingCharsArrays.java

@@ -0,0 +1,80 @@
+package Backtracking;
+
+import java.util.Arrays;
+
+public class sudokuSolverUsingCharsArrays {
+    public static void main(String[] args) {
+        char[][] charArray = {
+                {'5', '3', '.', '.', '7', '.', '.', '.', '.'},
+                {'6', '.', '.', '1', '9', '5', '.', '.', '.'},
+                {'.', '9', '8', '.', '.', '.', '.', '6', '.'},
+                {'8', '.', '.', '.', '6', '.', '.', '.', '3'},
+                {'4', '.', '.', '8', '.', '3', '.', '.', '1'},
+                {'7', '.', '.', '.', '2', '.', '.', '.', '6'},
+                {'.', '6', '.', '.', '.', '.', '2', '8', '.'},
+                {'.', '.', '.', '4', '1', '9', '.', '.', '5'},
+                {'.', '.', '.', '.', '8', '.', '.', '7', '9'}
+        };
+        solveSudoku(charArray);
+        System.out.println(Arrays.deepToString(charArray));
+    }
+
+    public static void solveSudoku(char[][] board) {
+        int[] complete = new int[1];
+        solver(board, 0, 0, complete);
+    }
+
+
+    public static void solver(char[][] board, int row, int col, int[] complete) {
+        if (row == board.length - 1 && col == board[0].length) {
+            complete[0] = 1;
+            return;
+        }
+        if (col == board[0].length) {
+            solver(board, row + 1, 0, complete);
+            return;
+        }
+        if (board[row][col] == '.') {
+            for (int i = 1; i <= 9; i++) {
+                if (isSafe(board, row, col, (char) (i + '0'))) {
+                    board[row][col] = (char) (i + '0');
+                    solver(board, row, col + 1, complete);
+                    if (complete[0] != 1) {
+                        board[row][col] = '.';
+                    }
+                }
+            }
+        } else {
+            solver(board, row, col + 1, complete);
+        }
+    }
+
+    private static boolean isSafe(char[][] board, int row, int col, char ch) {
+        // check the row
+        //row
+        for (int i = 0; i < 9; i++) {
+            if (board[i][col] == ch) {
+                return false;
+            }
+        }
+        //col
+        for (int i = 0; i < 9; i++) {
+            if (board[row][i] == ch) {
+                return false;
+            }
+        }
+
+        int sqrt = (int) (Math.sqrt(board.length));
+        int rowStart = row - row % sqrt;
+        int colStart = col - col % sqrt;
+
+        for (int r = rowStart; r < rowStart + sqrt; r++) {
+            for (int c = colStart; c < colStart + sqrt; c++) {
+                if (board[r][c] == ch) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+}

src/DynamicProgramming/LongestArithmeticSubsequence.java

@@ -0,0 +1,9 @@
+package DynamicProgramming;
+
+public class LongestArithmeticSubsequence {
+    public static void main(String[] args) {
+
+    }
+
+    
+}