void
stir (int n)
/* this stirs up the brew by exchanging n random key pairs */
{
int i, j;
int temp;
if (n < 0)
return;
while (n--)
{
i = rand () % 25;
do
j = rand () % 25;
while (j == i);
temp = mysquare.key[i];
mysquare.key[i] = mysquare.key[j];
mysquare.key[j] = temp;
}
}