David W. answered • 02/16/18
Tutor
4.7
(90)
Experienced Prof
There are only 3*2*1 = 6 possibilities:
D S P
D P S
S D P
S P D
P D S
P S D
"Sam is last" limits the choices to two:
D P S
P D S
"Dan is not behind Peter" further limits the choices to one:
D P S
First: Dan
Second: Peter
Third: Sam
David W.
Obviously, "exhaustive enumeration with elimination" is not taught well enough. Computer programs that consider all possible cases are often much simpler and much faster than complicated mathematical analysis [note: computers are very, very fast and very, very accurate!].
Today, I'm working on finding the only two factors of a very large prime number [see RSA Problem on Wikipedia]. Now, with elimination based on some characteristics of groups of prime numbers, I may find any two factors of the number. Now, actually, I don't need to prove that these are the ONLY two prime factors because the algorithm specs state that.
Application: I don't need to find your actual password to log in to your account, I just need to find any password that encrypts to the same value as your encrypted password (stored for comparison). This may be much, much easier than finding you actual password.
Report
02/16/18
Bobosharif S.
02/16/18