Valid sudoku

Hacktoberfest2022/ValidSudoku.java

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+import java.util.*;
+
+public class ValidSudoku{
+
+    public static void main(String []args){
+        char [][]sudoku=new char[][]{{'8','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'}};
+        System.out.println(isValidSudoku(sudoku));
+    }
+
+    //using bitmasking
+    public static boolean isValidSudoku(char[][] board) {
+        //arrays for marking numbers as visited for row,column,block
+        int brow[]=new int[9];
+        int bcol[]=new int[9];
+        int bblock[]=new int[9];
+        for(int i=0;i<9;i++){
+            for(int j=0;j<9;j++){
+                //if empty slot is encountered continue
+                if(board[i][j]=='.'){
+                    continue;
+                }
+                int val=(int)Math.pow(2,board[i][j]-'0');
+                //check if the value is already encountered in the row
+                if((brow[i]&val)>0){
+                    return false;
+                }
+                //if not encountered, mark it as encountered
+                brow[i]+=val;
+                //check if the value is already encountered in the column
+                if((bcol[j]&val)>0){
+                    return false;
+                }
+                //if not encountered, mark it as encountered
+                bcol[j]+=val;
+                int mod = (3 * (i / 3)) + (j / 3);
+                //check if the value is already encountered in the block
+                if((bblock[mod]&val)>0){
+                    return false;
+                }
+                //if not encountered, mark it as encountered
+                bblock[mod]+=val;
+            }
+        }
+        return true;
+    }
+
+}