Data commit

Task/Convex-hull/Jq/convex-hull-1.jq

@@ -0,0 +1,22 @@
+# ccw returns true if the three points make a counter-clockwise turn
+def ccw(a; b; c):
+  a as [$ax, $ay]
+  | b as [$bx, $by]
+  | c as [$cx, $cy]
+  | (($bx - $ax) * ($cy - $ay)) > (($by - $ay) * ($cx - $ax)) ;
+
+def convexHull:
+  if . == [] then []
+  else sort as $pts
+  # lower hull:
+  | reduce $pts[] as $pt ([];
+      until (length < 2 or ccw(.[-2]; .[-1]; $pt); .[:-1] )
+      | . + [$pt] )
+  # upper hull
+  | (length + 1) as $t
+  | reduce range($pts|length-2; -1; -1) as $i (.;
+      $pts[$i] as $pt
+      | until (length < $t or ccw(.[-2]; .[-1]; $pt); .[:-1] )
+      | . + [$pt])
+  | .[:-1]
+  end ;

Task/Convex-hull/Jq/convex-hull-2.jq

@@ -0,0 +1,8 @@
+def pts: [
+    [16,  3], [12, 17], [ 0,  6], [-4, -6], [16,  6],
+    [16, -7], [16, -3], [17, -4], [ 5, 19], [19, -8],
+    [ 3, 16], [12, 13], [ 3, -4], [17,  5], [-3, 15],
+    [-3, -9], [ 0, 11], [-9, -3], [-4, -2], [12, 10]
+];
+
+"Convex Hull: \(pts|convexHull)"