1 files changed, 82 insertions, 0 deletions
diff --git a/ch-1.pl b/ch-1.pl
new file mode 100644
index 0000000000..fa13f555f8
--- /dev/null
+++ b/ch-1.pl
@@ -0,0 +1,82 @@
+#!/usr/bin/perl
+
+use strict;
+use Data::Dumper;
+use List::Util qw/sum/;
+
+#  $steps : a string looks like DDDDRRRR,  DDRRRR, RDRDRD... 
+
+# my @ms = ([1,2,3], [4,5,6], [7,8,9]); # ms = shorthand of  matrixrows 
+# ans = 21
+# my @ms = ([1, 4, 7], [2, 0, 8], [3, 6, 9]); 
+# ans = 21
+ my @ms = ([1, 4, 7, 12], [2, 0, 8, 9], [3, 6, 9, 8]); 
+# ans = 26
+
+my @min_path;
+
+my $M = $#ms+1;
+my $N = $#{$ms[0]} + 1;
+my $totsteps = $M+$N-2;
+
+# a starting minimum
+my $refmin = sum @{$ms[0]};
+for (1..$M-1) {
+    $refmin += ${$ms[$_]}[$N-1];
+}
+
+sub go {
+    my $steps = $_[0];
+    my $hardship = $_[1];
+    $hardship += ${$ms[otimes($steps, 'D')]}[otimes($steps,'R')];
+    myseek($steps, $hardship) if ($hardship <= $refmin);
+}
+
+
+
+sub myseek {
+    my $steps = $_[0];
+    my $hardship = $_[1];
+    #    print $steps, " ", $hardship, "\n";    for testing
+    if ( (length $steps) < $totsteps ) {
+        go($steps.'D', $hardship) if $M-1 > otimes($steps, 'D');
+        go($steps.'R', $hardship) if $N-1 > otimes($steps, 'R');
+    } 
+    elsif ( $hardship <= $refmin) {
+        @min_path = tour($steps);
+        $refmin = $hardship;
+    }
+}
+
+
+sub otimes {
+    my $t = 0;
+    for my $x (split //, $_[0]) {
+        if ($x eq $_[1]) {
+            $t++;
+        }
+    }
+    return $t;
+}
+
+sub tour {
+    my $steps = $_[0];
+    my @_a = ( ${ms[0]}[0] );
+    my $x = 0;
+    my $y = 0;
+    my @ways = split //, $steps;
+    for my $w (@ways) {
+        if ($w eq 'D') {$y++;}
+        if ($w eq 'R') {$x++;}
+        push @_a, ${ms[$y]}[$x];
+    }
+#    push @_a, ${ms[$M-1]}[$N-1];
+    return @_a;
+}
+
+
+myseek('',${$ms[0]}[0]);
+
+print $refmin, "\n";
+print join " -> ", @min_path;
+print "\n";