世界一難しい数独

問題はこちら
http://matome.naver.jp/odai/2134127498258691101

#include <stdio.h>

struct SUUDOKU
{
	unsigned int table[9][9];
};

bool check(const struct SUUDOKU suudoku, const unsigned int i, const unsigned int x, const unsigned y)
{
	for(unsigned int px = 0; px < 9; px++)
	{
		if( i == suudoku.table[y][px] )
		{
			return false;
		}
	}
	for(unsigned int py = 0; py < 9; py++)
	{
		if( i == suudoku.table[py][x] )
		{
			return false;
		}
	}
	const unsigned int py_offset = (y/3)*3;
	const unsigned int px_offset = (x/3)*3;
	for(unsigned int py = py_offset; py < 3+py_offset; py++)
	{
		for(unsigned int px = px_offset; px < 3+px_offset; px++)
		{
			if( i == suudoku.table[py][px] )
			{
				return false;
			}
		}
	}
	return true;
}

bool solve(struct SUUDOKU suudoku, const unsigned int x, const unsigned int y)
{
	if( y == 9 )
	{
		for(unsigned int py = 0; py < 9; py++)
		{
			for(unsigned int px = 0; px < 9; px++)
			{
				printf("%d ",suudoku.table[py][px]);
			}
			printf("\n");
		}
		return true;
	}
	if( suudoku.table[y][x] != 0 )
	{
		return solve(suudoku, (x != 8) ? x+1: 0, (x != 8) ? y: y+1);
	}
	else
	{
		for(unsigned int i = 1; i <= 9; i++)
		{
			if( check(suudoku, i, x, y) == false )
			{
				continue;
			}
			suudoku.table[y][x] = i;
			bool ret = solve(suudoku, (x != 8) ? x+1: 0, (x != 8) ? y: y+1);
			if( ret == true )
			{
				return true;
			}
		}
		return false;
	}
}

int main()
{
	const struct SUUDOKU suudoku = {{
		{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}
	}};
	solve(suudoku, 0, 0);
	getchar();
	return 0;
}