gistfile1.txt

package sudoku;

import java.util.Random;

public class Puzzle {

  	// 9x9 puzzle
	private int puzzle[][] = new int[9][9];

	// generate a completely solved sudoku board
	public int[][] generate() {

		Random gen = new Random();

		// add each number to the board
		for (int x = 0; x < 9; x++) {
			for (int y = 0; y < 9; y++) {

				boolean isValid = false;

				// keep generating new numbers until a valid number is found
				while (isValid == false) {

					// generate random number 1-9
					int num = gen.nextInt(9) + 1;

					// check if number is valid
					if (checkRow(num, x) && checkCol(num, y)
							&& checkSection(num, x, y)) {

						// add number to the board
						puzzle[x][y] = num;

						// exit loop
						isValid = true;
					}
				}
			}
		}

		return puzzle;
	}

	// check each element of the row for num, if num is found return false
	private boolean checkRow(int num, int row) {

		for (int i = 0; i < 9; i++) {
			if (puzzle[row][i] == num) {
				return false;
			}
		}

		return true;
	}

	// check each element of the column for num, if num is found return false
	private boolean checkCol(int num, int col) {

		for (int i = 0; i < 9; i++) {
			if (puzzle[i][col] == num) {
				return false;
			}
		}

		return true;
	}

	// check each element of the section for num, if num is found return false
	private boolean checkSection(int num, int xPos, int yPos) {

		int[][] section = new int[3][3];
		section = getSection(xPos, yPos);

		for (int i = 0; i < 3; i++) {
			for (int j = 0; j < 3; j++) {
				if (section[i][j] == num)
					return false;
			}
		}
		return true;

	}

	// return the 3x3 section the given coordinates are in
	private int[][] getSection(int xPos, int yPos) {

		int[][] section = new int[3][3];
		int xIndex = 3 * (xPos / 3);
		int yIndex = 3 * (yPos / 3);

		for (int i = 0; i < 3; i++) {
			for (int j = 0; j < 3; j++) {
				section[i][j] = puzzle[xIndex + i][yIndex + j];
			}
		}

		return section;

	}
}