The following code is neither fast nor short. It also cannot find a solution
for input 8 8 8 9.
Need a solution always exist?
use strict;
die "Invalid number of chars" unless @ARGV == 4;
for (@ARGV) {
die "Invalid input $_" unless /^[1-9]$/;
}
my @vals=(undef,@ARGV); # Use 1 as first value;
my @ops =(undef,"*","+","-","/","");
my @op_ord_list = grep {/[1-5]{3}/} (111..555); #Duplicate
Ops OK
my @val_ord_list = grep {/[1-4]{4}/ && !/(.).*\1/} (1111..4444); #No
Duplicate Nums
for my $op_ord (@op_ord_list) {
my @op_index=split//,$op_ord;
for my $var_ord (@val_ord_list) {
my @val_index =split//,$var_ord;
#((a+b)+c)+d
test("((".
$vals[$val_index[0]]. $ops[$op_index[0]].
$vals[$val_index[1]].")".$ops[$op_index[1]].
$vals[$val_index[2]].")".$ops[$op_index[2]].
$vals[$val_index[3]]
);
#(a+(b+c))+d
test("(".
$vals[$val_index[0]]. $ops[$op_index[0]]."(".
$vals[$val_index[1]]. $ops[$op_index[1]].
$vals[$val_index[2]].")".$ops[$op_index[2]].
$vals[$val_index[3]]
);
#(a+b)+(c+d)
test("(".
$vals[$val_index[0]]. $ops[$op_index[0]].
$vals[$val_index[1]].")".$ops[$op_index[1]]."(".
$vals[$val_index[2]]. $ops[$op_index[2]].
$vals[$val_index[3]].")"
);
#a+(b+(c+d))
test(
$vals[$val_index[0]]. $ops[$op_index[0]]."(".
$vals[$val_index[1]]. $ops[$op_index[1]]."(".
$vals[$val_index[2]]. $ops[$op_index[2]].
$vals[$val_index[3]]."))"
);
#a+((b+c)+d)
test(
$vals[$val_index[0]]. $ops[$op_index[0]]."((".
$vals[$val_index[1]]. $ops[$op_index[1]].
$vals[$val_index[2]].")".$ops[$op_index[2]].
$vals[$val_index[3]].")"
);
}
}
print "Result not found\n";
sub test {
my $expr=shift;
return if $expr =~ /\d\(|\)\d/; # Ignore concat across ()'s
# print "Testing: $expr == ";
my $answer = eval $expr;
# print "$answer\n";
if ($answer==24) {
print "$expr == 24";
exit
}
}
> ----------------------------------------------------------------------
> Alistair McGlinchy, [EMAIL PROTECTED]
> Sizing and Performance, Central IT, ext. 5012, ph +44 20 7268-5012
> Marks and Spencer, 3 Longwalk Rd, Stockley Park, Uxbridge UB11 1AW, UK
>
> -----Original Message-----
> From: user who [SMTP:[EMAIL PROTECTED]]
> Sent: Friday, January 18, 2002 9:52 AM
> To: [EMAIL PROTECTED]
> Subject: make a 24(another practical problem)
>
>
> 4 numbers (all from 1-9) are given, make a formula(include +-*/()) for
> result 24. ex:
>
> 4, 2, 7, 5
> (4-2)*(7+5) = 24
>
> shortest/quickest solution?
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