Program builds but doesnt print anything

[xderkaderka]

Hello, I made a soduku puzzle solver in my C++ class, I got it to print the board, but once I made the actual solving part, it doesnt print anything.

#include <iostream>
using namespace std;

void print_board (int board[][10]);
bool isFinished (int board[][10]);
bool isNumValid (int board[][10], int row, int col, int num);
int main()
{
	// Initialize "board" array
	int board[10][10] = { {0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
						  {0, 7, 9, 6, 0, 0, 0, 3, 0, 0},
						  {0, 0, 0, 0, 0, 0, 6, 9, 0, 0},
						  {0, 8, 0, 0, 0, 3, 0, 0, 7, 6},
						  {0, 0, 0, 0, 0, 0, 5, 0, 0, 2},
						  {0, 0, 0, 5, 4, 1, 8, 7, 0, 0},
						  {0, 4, 0, 0, 7, 0, 0, 0, 0, 0},
						  {0, 6, 1, 0, 0, 9, 0, 0, 0, 8},
						  {0, 0, 0, 2, 3, 0, 0, 0, 0, 0},
						  {0, 0, 0, 9, 0, 0, 0, 1, 5, 4}};

	int numValidAnswers, validNum;
	do {
		for (int i = 1; i <= 9; i++)
		{
			for (int j = 1; j <= 9; j++)
			{
				if (board[i][j] == 0) // Empty spot; find a valid number
				{
					numValidAnswers = 0;
					for (int k = 1; k <= 9; k++)
					{
						if (isNumValid(board, i, j, k))
							{
								numValidAnswers++;
								validNum = k;
							}
					}
					if (numValidAnswers == 1)
					{
						board[i][j] = validNum;
					}
				}
			}
		}
	}
	while (!isFinished(board));

	// Print board
	print_board(board);
}

// Prints board according to array "board[10][10]"
void print_board (int board[][10])
{
	for(int i = 1; i < 10; i++)
	{
		for(int j = 1; j < 10; j++)
		{
			if (board[i][j] == 0) cout << " ";
			else cout << board[i][j];
			if (j == 3 || j == 6) cout << " | ";
		}
		cout << endl;
		if (i == 3 || i == 6) cout << "---------------" << endl;
	}
}

// Check if the board is finished or not
bool isFinished (int board[][10])
{
	for (int i = 1; i < 10; i++)
	{
		for (int j = 1; j < 10; j++)
		{
			if (board[i][j] == 0) return false;
		}
	}
	return true;
}

// Check if the current number is a valid number
bool isNumValid (int board[][10], int row, int col, int num)
{
	// Check row first
	for (int i = 1; i < 10; i++)
	{
		if (board[row][i] == num) return false;
	}

	// Check column next
	for (int i = 1; i < 10; i++)
	{
		if (board[i][col] == num) return false;
	}

	// Check subgroup
	// Get top row in this subgroup
	int topRow = row - ((row - 1) % 3);
	int topCol = col - ((row - 1) % 3);

	for (int i = topRow; i <= topRow + 2; i++)
	{
		for (int j = topCol; j <= topCol + 2; j++)
		{
			if (board[i][j] == num) return false;
		}
	}
	return true;
}

[john2]

You end up in an infinite loop. Cause you have a do-while loop that doesnt stop while there is a zero in the subokudokin puzzle. (whatever its called :S)
So how come you keep doing the do-while loop? Well, there isnt a garantee with this algoritm that you will find all the numbers needed for every 0-spot.

for (int k = 1; k <= 9; k++)
					{
						if (isNumValid(board, i, j, k))
							{
								numValidAnswers++;
								validNum = k;
							}
					}

what this piece of code does, is get the highest number between 1-9 that is a valid number. It doesnt mean its the right number for that position. You could deadlock the puzzle cause a wrong number in a sudoku puzzle (YES! i DO know the name :D) may cause another position to be unsolvable! ( If you play sudoku puzzles you know what I mean).

Conclusion: You get an infinite loop in the Do-while loop. Reason: wrong algoritm cause it never finds a suitable number for all the zeros in the puzzle!!!!