5 files changed, 138 insertions, 0 deletions
diff --git a/challenge-121/adam-russell/blog.txt b/challenge-121/adam-russell/blog.txt
new file mode 100644
index 0000000000..297696e467
--- /dev/null
+++ b/challenge-121/adam-russell/blog.txt
@@ -0,0 +1 @@
+http://www.rabbitfarm.com/cgi-bin/blosxom/perl/2021/07/18
diff --git a/challenge-121/adam-russell/blog1.txt b/challenge-121/adam-russell/blog1.txt
new file mode 100644
index 0000000000..4275477d70
--- /dev/null
+++ b/challenge-121/adam-russell/blog1.txt
@@ -0,0 +1 @@
+http://www.rabbitfarm.com/cgi-bin/blosxom/prolog/2021/07/18
diff --git a/challenge-121/adam-russell/perl/ch-1.pl b/challenge-121/adam-russell/perl/ch-1.pl
new file mode 100644
index 0000000000..21a610a169
--- /dev/null
+++ b/challenge-121/adam-russell/perl/ch-1.pl
@@ -0,0 +1,27 @@
+use strict;
+use warnings;
+##
+# You are given integers 0 <= $m <= 255 and 1 <= $n <= 8.
+# Write a script to invert $n bit from the end of the binary 
+# representation of $m and print the decimal representation 
+# of the new binary number.
+##
+ 
+sub flip_bit_n{
+    my($x, $n) = @_;
+    my $bits = substr(unpack("B32", pack("N", $x)), 24, 8);
+    my @bits = split(//, $bits);
+    $bits[@bits - $n] ^= 1; 
+    my $flipped_decimal = unpack("N", pack("B32", substr("0" x 32 . join("", @bits), -32)));
+    return $flipped_decimal; 
+}
+
+MAIN:{
+    my($M, $N);
+    $M = 12; 
+    $N = 3; 
+    print flip_bit_n($M, $N) . "\n";
+    $M = 18; 
+    $N = 4; 
+    print flip_bit_n($M, $N) . "\n";
+}  
diff --git a/challenge-121/adam-russell/perl/ch-2.pl b/challenge-121/adam-russell/perl/ch-2.pl
new file mode 100644
index 0000000000..c07d9c66d7
--- /dev/null
+++ b/challenge-121/adam-russell/perl/ch-2.pl
@@ -0,0 +1,68 @@
+use strict;
+use warnings;
+##
+# You are given a NxN matrix containing the distances between N cities.
+# Write a script to find a round trip of minimum length visiting 
+# all N cities exactly once and returning to the start.
+##
+use boolean;
+use AI::Genetic;
+
+use constant N => 20;
+
+my @matrix= ([0, 5, 2, 7], 
+             [5, 0, 5, 3],  
+             [3, 1, 0, 6],  
+             [4, 5, 4, 0]);  
+
+sub fitness{
+    my($genes) = @_;  
+    my $cost = 0;
+    return -1 if $genes->[0] != $genes->[@{$genes} - 1]; 
+    my @path = sort {$a <=> $b} @{$genes}[0 .. @{$genes} - 2];  
+    for my $i (0 .. (@path - 2)){
+        return -1 if $path[$i] == $path[$i + 1]; 
+    } 
+    for my $i (0 .. @{$genes} - 2){
+        $cost += $matrix[$genes->[$i]][$genes->[$i + 1]]; 
+    }  
+    return 1/$cost;  
+}
+
+sub terminate{
+    return true; 
+}
+
+MAIN:{
+    srand(121); 
+    my $aig = new AI::Genetic(
+        -fitness    => \&fitness,
+        -type       => "rangevector",
+        -population => 500,
+        -crossover  => 0.9,
+        -mutation   => 0.1,
+    );
+    my $genes = [];
+    for (0 .. N + 1){
+        push @{$genes}, [0, N]; 
+    }
+    @matrix = ();
+    for (0 .. N){
+        my $row = [];
+        for my $i (0 .. N){
+            push @{$row}, int(rand(N * 2 + 1));  
+        } 
+        push @matrix, $row; 
+    }
+    $aig->init(
+        $genes
+    );
+    $aig->evolve("tournamentUniform", 100000);
+    my $path = $aig->getFittest()->genes(); 
+    print join(",", @{$path}) . "\n"; 
+    my $cost;
+    for my $i (0 .. @{$path} - 2){
+        $cost += $matrix[$path->[$i]][$path->[$i + 1]]; 
+    }  
+    print "cost: $cost\n";  
+}
diff --git a/challenge-121/adam-russell/prolog/ch-1.p b/challenge-121/adam-russell/prolog/ch-1.p
new file mode 100644
index 0000000000..4acb12a5c6
--- /dev/null
+++ b/challenge-121/adam-russell/prolog/ch-1.p
@@ -0,0 +1,41 @@
+:-initialization(main).
+
+pad(Bits, Padded):-
+    length(Bits, L),
+    PadLength is 8 - L, 
+    length(Padding, PadLength),  
+    maplist(=(0), Padding),
+    append(Padding, Bits, Padded).  
+
+bits(N, Bits):-
+    bits(N, [], Bits).
+bits(0, Bits, Bits).    
+bits(N, Bit_Accum, Bits):-    
+    B is N /\ 1,
+    N0 is N >> 1,
+    bits(N0, [B|Bit_Accum], Bits).
+
+flip_nth_bit(N, Bits, NthFlipped):-
+    N0 is 9 - N, 
+    N1 is 8 - N, 
+    nth(N0, Bits, B),
+    Flipped is xor(B, 1),
+    length(Bits0, N1),
+    append(Bits0, [B|T], Bits), 
+    append(Bits0, [Flipped|T], NthFlipped).
+
+decimal(Bits, Decimal):-
+    decimal(Bits, 0, Decimal).
+decimal([], Decimal, Decimal).
+decimal([H|T], DecimalAccum, Decimal):-
+    length([H|T], B), 
+    D is (H * 2 ** (B - 1)) + DecimalAccum,
+    decimal(T, D, Decimal).  
+
+main:-
+    bits(12, B),
+    pad(B, Padded),  
+    flip_nth_bit(3, Padded, Flipped), 
+    decimal(Flipped, Decimal), 
+    write(Decimal), nl,
+    halt.