1 files changed, 162 insertions, 0 deletions
diff --git a/octans.raku b/octans.raku
new file mode 100755
index 0000000..fc070e9
--- /dev/null
+++ b/octans.raku
@@ -0,0 +1,162 @@
+#!/usr/bin/env raku
+
+use v6.d;
+use WWW;
+
+unit sub MAIN (
+    Str $url, #= url for Algot's crossword
+    Str :$dict = "/usr/share/dict/words", #= dictionary file
+    Bool :v($verbose), #= increase verbosity
+);
+
+my List @directions[4] = (
+    # $y, $x
+    ( +1, +0 ), # bottom
+    ( -1, +0 ), # top
+    ( +0, +1 ), # left
+    ( +0, -1 ), # right
+);
+
+# my List @puzzle = (
+#     <n a t k>,
+#     <i m e c>,
+#     <a r d e>,
+#     <t e c h>
+# );
+
+# my List @gray-squares = (3, 0), (2, 0); # $y, $x
+
+my @puzzle;
+my @gray-squares;
+
+my Str $toot_url;
+if $url.match("web/statuses") -> $match {
+    $toot_url = $match.replace-with("api/v1/statuses");
+} else {
+    $toot_url = "https://mastodon.art/api/v1/statuses/" ~ $url.split("/")[*-1];
+}
+
+say "Fetching: $toot_url" if $verbose;
+
+if (jget($toot_url)<media_attachments>[0]<description> ~~
+    # This regex gets the puzzle in $match.
+    / [[(\w [\*]?) \s*] ** 4] ** 4 $/) -> $match {
+    for 0 .. 3 -> $y {
+        for 0 .. 3 -> $x {
+            with $match[0][($y * 4) + $x].Str.lc -> $char {
+                if $char.ends-with("*") {
+                    @puzzle[$y][$x] = $char.comb[0];
+                    push @gray-squares, [$y, $x];
+                } else {
+                    @puzzle[$y][$x] = $char;
+                }
+            }
+        }
+    }
+}
+
+if $verbose {
+    say "Gray squares: ", @gray-squares;
+    say "Puzzle";
+    "    $_".say for @puzzle;
+}
+
+word: for $dict.IO.lines -> $word {
+    next word unless $word.chars >= 7;
+
+    start-pos: for @gray-squares -> $pos {
+        next start-pos unless $word.starts-with(
+            @puzzle[$pos[0]][$pos[1]]
+        );
+
+        next word unless $word.comb ⊆ @puzzle[*;*];
+
+        # Print the word if the search is successful.
+        say $word if word-search(@puzzle, $pos[0], $pos[1], $word);
+    }
+}
+
+# word-search performs a Depth-First search on @puzzle.
+sub word-search (
+    @puzzle, Int $y, Int $x,
+    # $count will keep the count of character's of $word present in
+    # the puzzle.
+    Str $word, Int $count = 1,
+    @visited? is copy
+     --> Bool
+) {
+    return True if $count == $word.chars;
+
+    # For each neighbor, we perform a Depth-First search to find the
+    # word.
+    neighbor: for neighbors(@puzzle, $y, $x).List -> $pos {
+        next neighbor if @visited[$pos[0]][$pos[1]];
+
+        if @puzzle[$pos[0]][$pos[1]] eq $word.comb[$count] {
+            # Here we're marking this position as True. This approach
+            # might cause us to miss possible solutions. If the puzzle
+            # is like so:
+            #
+            # a b e
+            # c a f
+            #
+            # And the word we're looking for is "cabefa". Then let's
+            # say that we go through the other 'a' first (bottom-mid
+            # 'a') & at this point it would be marked as True but the
+            # search would fail (correctly so).
+            #
+            # And after that failure we move to next neighbor which is
+            # top-left 'a'. The search goes on until we reach 'f' &
+            # get the list of f's neighbors which would return 'e' &
+            # bottom-mid 'a'. Now 'e' would be discarded because it
+            # was marked as visited but 'a' also has been marked as
+            # visited & it too would be discarded.
+            #
+            # This would cause us to miss solutions. So we just make
+            # it False again if the word wasn't found with this
+            # neighbor. After making it False, we move on to the next
+            # neighbor.
+
+            @visited[$pos[0]][$pos[1]] = True;
+            if word-search(
+                @puzzle, $pos[0], $pos[1],
+                $word, $count + 1,
+                @visited
+            ) {
+                return True;
+            } else {
+                @visited[$pos[0]][$pos[1]] = False;
+                next neighbor;
+            }
+        }
+    }
+    return False;
+}
+
+# neighbors returns the neighbors of given index. Neighbors are cached
+# in @neighbors array. This way we don't have to compute them
+# everytime neighbors subroutine is called for the same position.
+sub neighbors (
+    @puzzle, Int $y, Int $x --> List
+) {
+    state Array @neighbors;
+
+    if @puzzle[$y][$x] {
+        unless @neighbors[$y][$x] {
+            my Int $pos-x;
+            my Int $pos-y;
+
+            DIRECTION: for @directions -> $direction {
+                $pos-y = $y + $direction[0];
+                $pos-x = $x + $direction[1];
+
+                next DIRECTION unless @puzzle[$pos-y][$pos-x];
+                push @neighbors[$y][$x], [$pos-y, $pos-x];
+            }
+        }
+    } else {
+        @neighbors[$y][$x] = [];
+    }
+
+    return @neighbors[$y][$x];
+}