数独：9行9列表格，各行各列都填上1-9，且各行各列不能有重复数字

#include 
#include 
#include 

int main( int argc, char * argv[] )
{
	int pos = 0;
	int row,col;
	int val;
	int a[9][9] = {0};
	int count;
	
	srand(time(NULL));
	pos = 0;

LOOP_OUT:
	while(pos<=80)  //pos 0 ==> a[0][0],  pos 80 ==> a[8][8]
	{
		row = pos/9;
		col = pos%9;
		val = random()%9 + 1;

		for(count = 1; count<= 9; count++)
		{
			if( check_ok(a,pos,val) )
			{
				a[row][col] = val;
				pos++;
				goto LOOP_OUT;
			}
			else		//if val is 5, we try 6,7,8,9,1,2,3,4
				val = val%9+1;
		}
		// this pos , val failed
		if(pos >=9)
			pos -=9; //pos fail, back 1 line
	}

	//print result
	for( row = 0; row<9; row++)
	{
		for( col = 0; col<9; col++)
			printf("%d ", a[row][col]);
		printf("\n");
	}
	return 0;
}

int check_ok(int a[9][9], int pos, int value)
{
	int row  = pos/9;
	int col  = pos%9;
	int i,j;

	j = col;
	for( i=row-1; i>=0;i--)
	{
		if( a[i][j] == value )
			return 0;
	}

	i = row;
	for( j=col-1; j>=0; j--)
	{
		if( a[i][j] == value )
			return 0;
	}
	return 1;
}

1 5 2 3 6 8 7 4 9 
4 6 9 7 8 1 2 3 5 
2 8 1 4 9 3 5 6 7 
8 2 3 5 4 6 9 7 1 
9 7 4 6 1 5 8 2 3 
3 9 5 1 7 2 4 8 6 
5 3 8 9 2 7 6 1 4 
6 1 7 8 5 4 3 9 2 
7 4 6 2 3 9 1 5 8