From dcbd9d85545b1c4ab831a7d00589425676fe24e2 Mon Sep 17 00:00:00 2001
From: sreenidhi3 <sreenidhi.bendre@gmail.com>
Date: Sat, 3 Oct 2020 13:44:19 +0530
Subject: [PATCH] Created  Backtracking folder and added sudoku solver

---
 Backtracking/sudokuSolver.java | 71 ++++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)
 create mode 100644 Backtracking/sudokuSolver.java

diff --git a/Backtracking/sudokuSolver.java b/Backtracking/sudokuSolver.java
new file mode 100644
index 00000000..c8d2fc2d
--- /dev/null
+++ b/Backtracking/sudokuSolver.java
@@ -0,0 +1,71 @@
+import java.util.Arrays;
+
+public class Sudoku {
+    public static void main(String[] args) {
+    int[][] board ={ {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} };
+    sudoku(board, 0,0);
+    }
+    public static void sudoku(int[][] board, int row, int col){
+        if (row == 9){
+            //print board
+            for (int i = 0; i < 9; i++) {
+                System.out.println(Arrays.toString(board[i]));
+            }
+            return;
+        }
+        //completed the row
+        if (col == 9){
+            sudoku(board, row+1,0);
+            return;
+        }
+        //if current ite is blank
+        if(board[row][col]==0){
+            //process
+            for (int i = 1; i <= 9; i++) {
+                if(isSafe(board, row, col, i)){
+                    board[row][col] = i;
+                    sudoku(board, row, col+1);
+                    board[row][col] = 0;
+                }
+            }
+        } else {
+            sudoku(board, row, col+1);
+        }
+    }
+
+    public  static boolean isSafe(int[][] board, int row, int col, int val){
+        //check row
+        for (int c = 0; c <9 ; c++) {
+            if(board[row][c] == val){
+                return false;
+            }
+        }
+        //check column
+        for (int r = 0; r<9; r++){
+            if (board[r][col] == val){
+                return false;
+            }
+        }
+
+        //check current box
+        int rowChunk = row/3;
+        int colChunk = col/3;
+
+        for (int a = rowChunk*3; a <(rowChunk+1)*3 ; a++) {
+            for (int b = colChunk*3; b < (colChunk+1)*3 ; b++) {
+                if(board[a][b] == val){
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+}
\ No newline at end of file