use strict; use warnings; use Test::More 'no_plan'; $| = 1; my %cache; sub exact { my ($amount, @bills) = @_; return $cache{$amount} if defined $cache{$amount}; return 1 if !$amount; return 0 if $amount < 0; foreach my $bill (@bills) { return $cache{$amount} = 1 if exact($amount - $bill, @bills) } return $cache{$amount} = 0; } sub largest { %cache = (); my @bills = @_; my $smallest = $bills [0]; return -1 if $smallest == 1; my $start = 0; my $prev = 0; for (my $t = 1; 1; $t++) { if (exact($t, @bills)) { if ($prev) { if ($t - $start + 1 == $smallest) {return $start - 1} } else {$start = $t} $prev = 1; } else { $prev = 0; } } } is (largest(6,9,20), 43); is (largest(3,5), 7); is (largest(6,11,20), 27); is (largest(17,18,19,20), 101); is (largest(2,3,5,10), 1); is (largest(1000,1001,1002,1003,1004,1005), 199999); __END__ ok 1 ok 2 ok 3 ok 4 ok 5 ok 6 1..6