Coding a Java Sudoku Solver - Java Programming

In this video, we'll write a program that can solve Sudoku puzzles using a recursive backtracking algorithm. Hope you like the video!
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[@willtollefson]

Here's the full source code for convenience 🙂
import java.util.stream.IntStream;
public class SudokuSolver {
private static final int BOX_SIZE = 3;
private static final int GRID_SIZE = BOX_SIZE * BOX_SIZE;
public static void main(String[] args) {
int[][] board = {
{0, 0, 0, 6, 0, 0, 4, 0, 0},
{7, 0, 0, 0, 0, 3, 6, 0, 0},
{0, 0, 0, 0, 9, 1, 0, 8, 0},
{0, 0, 0, 0, 0, 0, 0, 0, 0},
{0, 5, 0, 1, 8, 0, 0, 0, 3},
{0, 0, 0, 3, 0, 6, 0, 4, 5},
{0, 4, 0, 2, 0, 0, 0, 6, 0},
{9, 0, 3, 0, 0, 0, 0, 0, 0},
{0, 2, 0, 0, 0, 0, 1, 0, 0}
};
if (solve(board)) {
System.out.println("Yay!");
printResult(board);
} else {
System.out.println("Oops :(");
}
}
private static void printResult(int[][] board) {
for (int row = 0; row < GRID_SIZE; row++) {
if ((row % BOX_SIZE == 0) && (row != 0)) {
System.out.println("-----------------------------");
}
for (int col = 0; col < GRID_SIZE; col++) {
if ((col % BOX_SIZE == 0) && (col != 0)) {
System.out.print("|");
}
final int cellValue = board[row][col];
System.out.print(" ");
if (cellValue == 0) {
System.out.print(" ");
} else {
System.out.print(cellValue);
}
System.out.print(" ");
}
System.out.println();
}
}
private static boolean allowedInRow(int[][] board, int row, int number) {
return IntStream.range(0, GRID_SIZE)
.noneMatch(col -> board[row][col] == number);
}
private static boolean allowedInCol(int[][] board, int col, int number) {
return IntStream.range(0, GRID_SIZE)
.noneMatch(row -> board[row][col] == number);
}
private static boolean allowedInBox(int[][] board, int row, int col, int number) {
final int boxCol = col - (col % BOX_SIZE);
final int boxRow = row - (row % BOX_SIZE);
for (int i = 0; i < BOX_SIZE; i++) {
for (int j = 0; j < BOX_SIZE; j++) {
if (board[boxRow + i][boxCol + j] == number) {
return false;
}
}
}
return true;
}
private static boolean isAllowed(int[][] board, int row, int col, int number) {
return allowedInRow(board, row, number) &&
allowedInCol(board, col, number) &&
allowedInBox(board, row, col, number);
}
private static boolean solve(int[][] board) {
for (int row = 0; row < GRID_SIZE; row++) {
for (int col = 0; col < GRID_SIZE; col++) {
if (board[row][col] == 0) {
for (int num = 1; num

[@DenaTollefson]

Wow Will what a fantastic tutorial on how to write a Java program to solve a Sudoku puzzle! Awesome!

[@willtollefson]

Glad you liked it!

[@pablopronsky7364]

Amazing!!!!! I'll try to make the sudoku on my own now haha
Hope you are doing great, Professor!
Pablo.

[@willtollefson]

Hahaha sounds good, Pablo! I'm doing well here in the US. Hope its going well in Argentina!

[@pablopronsky7364]

@@willtollefson Tomorrow (sunday) we have elections and we decide between North Korea and the Free World. Hope everything goes well for us!
Thanks for asking Professor! Have a great week!!!!