---
title: "Sudoku puzzle implemented in Java"  
description: "Sudoku puzzle implemented in Java"  
author: "Anonymous User"  
published: 2015-04-23  
updated: 2015-04-23  
canonical: https://www.mindstick.com/forum/23113/sudoku-puzzle-implemented-in-java  
category: "java"  
tags: ["java"]  
reading_time: 4 minutes  

---

# Sudoku puzzle implemented in Java

There is a puzzle that is becoming very popular called **SuDuko**. It is like a [cross](https://www.mindstick.com/forum/33892/how-to-handle-cross-thread-exception-in-winforms)-word puzzle but with digits 1 thru 9 instead of letters. It started in the U.S. and became very popular in Japan\
The [board](https://www.mindstick.com/blog/12258/preparation-tips-for-cbse-class-12-board-exam) has 9 X 9 boxes laid out in a square. Each box has 9 [fields](https://www.mindstick.com/forum/159126/sql-query-for-all-tables-and-fields-in-an-oracle-db) laid out in a 3 x 3 square. Some of the fields are initiated with numbers. An easy [game](https://www.mindstick.com/articles/44320/web-development-trends-that-are-changing-the-game) has many initial numbers and a more difficult game has fewer initial numbers.0,0,0, 0,0,0, 0,1,20,0,0, 0,5,1, 3,8,00,8,0, 0,0,6, 0,0,0\
1,0,0, 2,4,0, 0,7,00,0,0, 0,3,0, 0,0,00,7,0, 0,6,5, 0,0,3\
0,0,0, 4,0,0, 0,2,00,5,9, 6,8,0, 0,0,08,1,0, 0,0,0, 0,0,0\
The object of the puzzle is to [replace](https://yourviews.mindstick.com/view/81330/cow-antibody-research-in-usa-a-step-ahead-to-replace-plasma-therapy) the 0's (blanks) with numbers 1 thru 9 such that each row, each [column](https://www.mindstick.com/forum/33860/how-to-calculate-column-summary-in-sql-server) and each 3 x 3 box has only the numbers 1 thru 9. Can [anyone](https://www.mindstick.com/articles/23207/how-to-find-the-best-fit-job-for-anyone) write a [Java](https://www.mindstick.com/articles/12214/web-development-company-in-india-laid-on-the-foundation-of-concrete-java-programming) [code](https://yourviews.mindstick.com/view/85458/alan-turing-the-mastermind-behind-cracking-the-enigma-code-during-world-war-ii) that would solve this very hard puzzle with only 25 [starting](https://www.mindstick.com/blog/12024/things-you-need-to-know-when-starting-your-own-business) numbers\
\

## Replies

### Reply by Anonymous User

```
public class sudoku {      // Is every number 1-9 in the given rectangle 0..1 times?    public static boolean isRectangleLegal(int[][] board, int x1, int x2, int y1, int y2, String errormsg) {boolean[] isPresent = {false, false, false, false, false, false, false, false, false, false};  for (int x=x1; x<=x2; x++) {    for (int y=y1; y<=y2; y++) {if (board[x][y] > 0) {    if (isPresent[board[x][y]]) {//System.out.println(errormsg + ": multiple " + board[x][y] + "s");return false;    }    isPresent[board[x][y]] = true;}    }}return true;    }      public static boolean isLegal(int[][] board) {// Check the nine blocks.if (!isRectangleLegal(board, 0, 2, 0, 2, "Block 1")) return false;if (!isRectangleLegal(board, 3, 5, 0, 2, "Block 2")) return false;if (!isRectangleLegal(board, 6, 8, 0, 2, "Block 3")) return false;if (!isRectangleLegal(board, 0, 2, 3, 5, "Block 4")) return false;if (!isRectangleLegal(board, 3, 5, 3, 5, "Block 5")) return false;if (!isRectangleLegal(board, 6, 8, 3, 5, "Block 6")) return false;if (!isRectangleLegal(board, 0, 2, 6, 8, "Block 7")) return false;if (!isRectangleLegal(board, 3, 5, 6, 8, "Block 8")) return false;if (!isRectangleLegal(board, 6, 8, 6, 8, "Block 9")) return false;  // check the nine columnsif (!isRectangleLegal(board, 0, 0, 0, 8, "Column 0")) return false;if (!isRectangleLegal(board, 1, 1, 0, 8, "Column 1")) return false;if (!isRectangleLegal(board, 2, 2, 0, 8, "Column 2")) return false;if (!isRectangleLegal(board, 3, 3, 0, 8, "Column 3")) return false;if (!isRectangleLegal(board, 4, 4, 0, 8, "Column 4")) return false;if (!isRectangleLegal(board, 5, 5, 0, 8, "Column 5")) return false;if (!isRectangleLegal(board, 6, 6, 0, 8, "Column 6")) return false;if (!isRectangleLegal(board, 7, 7, 0, 8, "Column 7")) return false;if (!isRectangleLegal(board, 8, 8, 0, 8, "Column 8")) return false;  // check the nine rowsif (!isRectangleLegal(board, 0, 8, 0, 0, "Row 0")) return false;if (!isRectangleLegal(board, 0, 8, 1, 1, "Row 1")) return false;if (!isRectangleLegal(board, 0, 8, 2, 2, "Row 2")) return false;if (!isRectangleLegal(board, 0, 8, 3, 3, "Row 3")) return false;if (!isRectangleLegal(board, 0, 8, 4, 4, "Row 4")) return false;if (!isRectangleLegal(board, 0, 8, 5, 5, "Row 5")) return false;if (!isRectangleLegal(board, 0, 8, 6, 6, "Row 6")) return false;if (!isRectangleLegal(board, 0, 8, 7, 7, "Row 7")) return false;if (!isRectangleLegal(board, 0, 8, 8, 8, "Row 8")) return false;return true;    }      public static boolean solve(int[][] board) { // Find a position that's still empty.for (int x=0; x<9; x++) {    for (int y=0; y<9; y++) {if (board[x][y] == 0) {      // Try each possibile value in this space    // and see if the rest of the puzzle can be filled in.    for (board[x][y]=1; board[x][y]<=9; board[x][y]++) {if (isLegal(board) && solve(board)) {    return true;}    }      // There is no value that we can put in the first    // empty space that was found, so the puzzle is    // unsolvable given the values put in up to this    // point.    board[x][y] = 0;    return false;}    }}  // There were no empty spaces to fill in, so the// puzzle must be solved.return true;    }      public static void printBoard(int[][] board) {        for (int x=0; x<9; x++) {    System.out.println(x%3==0 ? "+-----+-----+-----+" : "|     |     |     |");    for (int y=0; y<9; y++)System.out.print((y%3==0 ? "|" : " ") + board[x][y]);     System.out.println("|");}System.out.println("+-----+-----+-----+");    }      public static void main(String[] argv) {  int board[][] = {{0,0,0, 0,0,0, 0,1,2},{0,0,0, 0,5,1, 3,8,0},{0,8,0, 0,0,6, 0,0,0}, {1,0,0, 2,4,0, 0,7,0},{0,0,0, 0,3,0, 0,0,0},{0,7,0, 0,6,5, 0,0,3}, {0,0,0, 4,0,0, 0,2,0},{0,5,9, 6,8,0, 0,0,0},{8,1,0, 0,0,0, 0,0,0} };  if (solve(board))    printBoard(board);else    System.out.println("no solution");    }}
```


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Original Source: https://www.mindstick.com/forum/23113/sudoku-puzzle-implemented-in-java

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