initialize

Sudoku.java

@@ -0,0 +1,114 @@
+public class Sudoku {
+
+    private  int[][] board;
+
+    //constructor
+    public Sudoku (int[][] board) {
+        this.board = board;
+    }
+
+    //get board
+    public int[][] getBoard() {
+        return board;
+    }
+
+
+    //solve method helper
+    public void solve() {
+        solve(0,0);
+    }
+
+    //solves the next position and returns true if it is possible
+    private boolean nextPos(int row, int col) {
+
+        if (col < 8) {
+            return solve(row, col + 1);
+        } else {
+            return solve(row + 1, 0);
+        }
+    }
+
+    //solves the sudoku
+    private boolean solve(int row, int col) {
+
+        //base case
+        if(row > 8) {
+            return true;
+        }
+
+        if(board[row][col] != 0) {
+            if(check(row, col, board[row][col])) {
+                return nextPos(row, col);
+            }
+        }
+
+
+        int num = board[row][col];
+
+        //checks each number from 1 to 9
+        for(int i = 1; i < 10; i++) {
+
+            if(check(row, col, i)) {
+
+                board[row][col] = i;
+                if(nextPos(row, col)) {
+                    return true;
+                }
+
+
+
+            }
+
+            //clears the previous positions
+            board[row][col] = 0;
+
+        }
+
+
+        return false;
+    }
+
+    //checks for each scenario
+    public boolean check(int row, int col, int x) {
+
+        //checks for rows and  column
+        for(int i = 0; i < board.length; i++) {
+            if(i != row && board[i][col] == x) {
+                return false;
+            }
+
+            if(i != col && board[row][i] == x) {
+                return false;
+            }
+        }
+
+
+        int squareRow = (row/3) * 3;
+        int squareCol = (col/3) * 3;
+
+
+        //checks for 3x3
+        for(int i = squareRow; i < squareRow+3; i++) {
+            for(int j = squareCol; j < squareCol+3; j++) {
+                if((j != col || i != row) && board[i][j] == x) {
+                    return false;
+                }
+            }
+        }
+
+        return true;
+    }
+
+
+
+    //prints the board
+    public void print() {
+        for(int r = 0; r < board.length; r++) {
+            for (int c = 0; c < board[r].length; c++)
+                System.out.print(board[r][c] + " ");
+            System.out.println();
+        }
+    }
+
+
+}

SudokuClient.java

@@ -0,0 +1,89 @@
+
+import java.io.IOException;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.util.Scanner;
+
+public class SudokuClient {
+    public static void main(String[] args) throws MalformedURLException {
+
+
+
+        //World's hardest sudoku
+        int[][] board = {
+                {8,0,0,0,0,0,0,0,0},
+                {0,0,3,6,0,0,0,0,0},
+                {0,7,0,0,9,0,2,0,0},
+                {0,5,0,0,0,7,0,0,0},
+                {0,0,0,0,4,5,7,0,0},
+                {0,0,0,1,0,0,0,3,0},
+                {0,0,1,0,0,0,0,6,8},
+                {0,0,8,5,0,0,0,1,0},
+                {0,9,0,0,0,0,4,0,0},
+        };
+
+        Sudoku test = new Sudoku(board);
+
+        test.solve();
+        test.print();
+
+
+        //Project Euler Problem 96
+        URL file = new URL("https://projecteuler.net/project/resources/p096_sudoku.txt");
+        int sum = 0;
+
+        //whole text file
+        String s = "";
+
+        try {
+            Scanner scanner = new Scanner(file.openStream());
+
+
+            while(scanner.hasNextLine()) {
+
+               s += scanner.nextLine() + "\n";
+
+
+            }
+
+        } catch (IOException e) {
+            System.out.println(e);
+        }
+
+        //Array of lines of the text
+        String[] lines = s.split(System.getProperty("line.separator"));
+
+        //Goes over each line
+        for(int i = 0; i < lines.length; i++) {
+
+            int[][] sudoku96 = new int[9][9];
+
+            //If line is not a title, stores it in a 2D array
+            if(lines[i].contains("Grid")) {
+                for(int r = 0; r < sudoku96.length; r++) {
+                    for(int c = 0; c < sudoku96[r].length; c++) {
+
+                        sudoku96[r][c] = Character.getNumericValue(lines[i+ r + 1].charAt(c));
+
+
+                    }
+                }
+
+                //Sudoku class
+                Sudoku sudokuSolver = new Sudoku(sudoku96);
+                sudokuSolver.solve();
+                sudoku96 = sudokuSolver.getBoard();
+                String digits = sudoku96[0][0] + "" + sudoku96[0][1] + "" + sudoku96[0][2];
+                sum += Integer.parseInt(digits);
+
+            }
+
+
+
+        }
+
+        System.out.println();
+        System.out.println(sum);
+
+    }
+}