1 files changed, 64 insertions, 0 deletions
diff --git a/challenge-144/david-santiago/raku/ch-1.raku b/challenge-144/david-santiago/raku/ch-1.raku
new file mode 100755
index 0000000000..422fb4955f
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+++ b/challenge-144/david-santiago/raku/ch-1.raku
@@ -0,0 +1,64 @@
+#!/usr/bin/env raku
+
+sub sieve-of-atkin(Int $limit --> List){
+    my @sieve;
+    my @prime-list = (2,3);
+    
+    my $x = 1;
+    while $x ** 2 < $limit {
+	my $y = 1;
+	while $y ** 2 < $limit {
+
+	    my $n = 4 * $x ** 2 + $y ** 2;
+	    
+	    if $n <= $limit && ($n % 12 == 1 || $n % 12 == 5) {
+		@sieve[$n] = @sieve[$n] ?? False !! True;
+	    }
+
+	    $n = 3 * $x ** 2 + $y ** 2;
+	    if $n <= $limit && $n % 12 == 7 {
+		@sieve[$n] = @sieve[$n] ?? False !! True;
+	    }
+
+	    $n = (3 * $x ** 2 ) - $y ** 2;
+	    if $n <= $limit && $x > $y && $n % 12 == 11 {
+		@sieve[$n] = @sieve[$n] ?? False !! True;
+	    }
+	    $y++;
+	}
+	$x++;
+    }
+    # Mark all multiples of squares as non-prime
+    my $r = 5;
+    while $r ** 2 < $limit {
+	if @sieve[$r] {
+	    loop ( my $i = $r**2; $i < $limit; $i += $r**2 ) {
+		@sieve[$i] = False;
+	    }
+	}
+	$r++;
+    }
+
+    for @sieve.kv -> $index, $is-prime {
+	@prime-list.append($index) if $is-prime;
+    }
+
+    return @prime-list;
+}
+
+
+sub MAIN() {
+    my @prime-list := sieve-of-atkin(100);
+    my @combinations = (|@prime-list xx 2 ).flat.combinations(2);
+    
+    my %semi-primes;
+    for @combinations -> @comb {
+	my $candidate = @comb[0]*@comb[1];
+	%semi-primes{$candidate} = (@comb[0],@comb[1]) if $candidate < 100;
+    }
+    
+    for %semi-primes.keys.sort {
+	say "$_ is Semiprime as $_ = {%semi-primes{$_}.join(' x ')}";
+    }
+    
+}