# by bliako on 30/08/2021 # for https://perlmonks.org/?node_id=11136212 use bigint qw/hex/; use Digest::SHA1 qw/sha1 sha1_hex/; my $digest_hex = sha1_hex('blah blah blah'); my $answer = hex($digest_hex); print "$0 : starting with this number: $answer.\n"; my $min = 0; my $max = 2**160; my $num_guesses = 0; my ($guess, $diff); while( ++$num_guesses ){ $guess = $min + ($max - $min) / 2.0; $diff = $guess - $answer; print "entering at guess number $num_guesses, current range:\n min: $min\n max: $max\n answer: $answer\n guess: $guess\n diff: $diff\n"; if( $guess < $answer ){ print "your guess ($guess) needs to go higher ...\n"; $min = int($guess); } elsif( $guess > $answer ){ print "your guess ($guess) needs to go lower ...\n"; $max = int($guess); } else { print "bingo in $num_guesses guesses! the answer was: $digest_hex and your guess was ".bigint_to_hex($guess)." ($guess).\n"; last; } } sub bigint_to_hex { # graduitously ripped off from Ben Aveling's answer in # https://stackoverflow.com/questions/828462/how-can-i-sprintf-a-big-number-in-perl # because sprintf("%x", bigint) does not work sadly... my $inp = shift; my $out = ""; while($inp){ my $chunk=$inp & 0xf; $inp >>= 4; $out = sprintf("%x",$chunk).$out; } return $out; }