OJ Board

I just like to point out an alternative to using the array with st[0] = 'A', st[1] = 'a', etc. I would recommend a function, like this one:

bool isLower(char a, char b)
{
if (tolower(a) == tolower(b)) return (a < b);
else return (tolower(a) < tolower(b));
}

It gives the order you're looking for ...

Try http://www-cs-faculty.stanford.edu/~knuth/fasc2b.ps.gz. This is a preview on a chapter on permutations in Knuth's Art of Computer Programming. Should be the definite guide