Week 281 Task 2

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diff --git a/challenge-281/cheok-yin-fung/perl/ch-2.pl b/challenge-281/cheok-yin-fung/perl/ch-2.pl
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+# The Weekly Challenge 281
+# Task 2 Knight's Move
+
+use v5.30.0;
+use warnings;
+use List::Util qw/min/;
+
+sub small_dist {
+    my $pos_a = $_[0];
+    my $pos_b = $_[1];
+    my $diff0 = abs($pos_a->[0]-$pos_b->[0]);
+    my $diff1 = abs($pos_a->[1]-$pos_b->[1]);
+    if ($diff0 == 1 && $diff1 == 2 || $diff0 == 2 && $diff1 == 1) 
+        {return 1;}
+    if ($diff0 == 0 && $diff1 == 2 || $diff0 == 2 && $diff1 == 0)
+        {return 2;} 
+    if ($diff0 == 0 && $diff1 == 1 || $diff0 == 1 && $diff1 == 0)
+        {return 3;}
+    if ($diff0 == 1 && $diff1 == 1) { 
+        if (is_corner($pos_a)|| is_corner($pos_b)) {
+            return 4;
+        }
+        else {
+            return 2;
+        }
+    }
+    if ($diff0 == 2 && $diff1 == 2) {
+        return 4;
+    }
+}
+
+sub km {
+    my $targt = $_[0];
+    my $begin = $_[1];
+    my $pos_a = [ord(substr($begin,0,1))-ord("a"), substr($begin,1,2)-1];
+    my $pos_b = [ord(substr($targt,0,1))-ord("a"), substr($targt,1,2)-1];
+    return dist($pos_a, $pos_b);
+}
+
+sub dist {
+    my $pos_a = $_[0];
+    my $pos_b = $_[1];
+    if ((abs($pos_a->[0]-$pos_b->[0]) <= 2) && (abs($pos_a->[1]-$pos_b->[1]) <= 2)) {
+        return small_dist($pos_a, $pos_b);
+    }
+    my $cur_tc_dist = taxicab_dist($pos_a, $pos_b);
+    my @px = (+2, +2, +1, +1, -1, -1, -2, -2);
+    my @py = (+1, -1, +2, -2, +2, -2, +1, -1);
+    my @nxt;
+    for my $k (0..7) {
+        my $npx = $pos_b->[0]+$px[$k];
+        my $npy = $pos_b->[1]+$py[$k];
+        if ($npx < 0 || $npx > 7) {next;}
+        if ($npy < 0 || $npy > 7) {next;}
+        my $tc_dist = taxicab_dist($pos_a, [$npx, $npy]);
+        push @nxt, [$npx, $npy] if $tc_dist < $cur_tc_dist;
+    }
+    if (scalar @nxt == 1) {
+        return ( 1 + dist($pos_a, $nxt[0]) );
+    } else {
+        my @choice_val;
+        for (0..$#nxt) {
+            $choice_val[$_] = 1 + dist($pos_a, $nxt[$_]);
+        }
+        #say(chr(ord('a')+$pos_b->[0]).(1+$pos_b->[1])." ", min(@choice_val));
+        return min(@choice_val);
+    }
+}
+sub taxicab_dist {
+    my $pos_a = $_[0];
+    my $pos_b = $_[1];
+    my $taxicab_dist = 
+        abs($pos_a->[0]-$pos_b->[0])
+                +
+        abs($pos_a->[1]-$pos_b->[1]);
+    return $taxicab_dist;
+}
+
+sub is_corner {
+    my $pos = $_[0];
+    if (($pos->[0] == 0 || $pos->[0] == 7) 
+            &&
+       ($pos->[1] == 0 || $pos->[1] == 7)) 
+    {
+       return 1;
+    }
+    return 0;
+}
+