Create ch-1.pl

1 files changed, 71 insertions, 0 deletions

diff --git a/challenge-069/cheok-yin-fung/perl/ch-1.pl b/challenge-069/cheok-yin-fung/perl/ch-1.pl
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+++ b/challenge-069/cheok-yin-fung/perl/ch-1.pl
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+#!/usr/bin/perl
+#
+# Perl Weekly Challenge #069 Task 1 - Strobogrammatic Number
+# Usage: ch-1.pl $A $B,  where 1 <= $A <= $B <= 10^15
+# the following code goes "out of memory" around $B >= 10^11
+
+use Algorithm::Combinatorics qw/variations_with_repetition/;
+use strict;
+use warnings;
+
+sub rt180 {
+    my @digits = split // , $_[0];
+    my @newdigits = ();
+    for (@digits) {
+        my $nex;
+        $nex = 1 if $_ == 1;
+        $nex = 0 if $_ == 0;
+        $nex = 8 if $_ == 8;
+        $nex = 9 if $_ == 6;
+        $nex = 6 if $_ == 9;
+        unshift @newdigits, $nex;    
+    }
+    return join '', @newdigits;
+}
+
+my @ans = ();
+my $begin = 3;
+my $end = 4;
+if ($ARGV[0] and $ARGV[1]) {
+    $begin = $ARGV[0];
+    $end = $ARGV[1]; 
+}
+
+my $sbegin = length $begin;
+my $send = length $end;
+
+if ($sbegin == 1) {
+    $sbegin = 2;
+    if ($send != 1) {
+        @ans = ($begin..9);
+    } else {
+        @ans = ($begin..$end);
+    }
+}
+
+for my $s ($sbegin .. $send) {
+    foreach my $r (qw/1 6 8 9/) {
+        my $o = variations_with_repetition([0, 1, 6, 8, 9],$s-1);
+        while (my $y = $o->next) {
+            my $string = $r.(join '', @{$y});
+            push @ans, $string if $string eq rt180($string);
+        }
+    }
+}
+
+
+for (@ans) {
+    print $_, " " if $_ <= $end and $_ >= $begin;
+}
+
+
+print "\n";
+
+
+# $ time perl ch-1.pl 100000001 999999999 > ans069.txt (10^8+1 to 10^9-1)
+# 
+# real	0m9.288s
+# user	0m9.282s
+# sys	0m0.004s
+
+# not very satisfactory