Shorter solution

Author: w8r

src/pack/enclose.js

@@ -8,28 +8,16 @@ export default function(circles) {
 export function packEncloseRandom(circles, random) {
   var i = 0, n = (circles = shuffle(Array.from(circles), random)).length, B = [], p, e;
 
-  var minX = Number.MAX_VALUE, minY = Number.MAX_VALUE;
-  var maxX = Number.MIN_VALUE, maxY = Number.MIN_VALUE;
-  for (var k = 0; k < n; ++k) {
-    var c = circles[k];
-    minX = Math.min(minX, c.x - c.r);
-    minY = Math.min(minY, c.y - c.r);
-    maxX = Math.max(maxX, c.x + c.r);
-    maxY = Math.max(maxY, c.y + c.r);
-  }
-
-  var cx = (minX + maxX) / 2, cy = (minY + maxY) / 2;
-
   while (i < n) {
     p = circles[i];
     if (e && enclosesWeak(e, p)) ++i;
-    else e = encloseBasis(B = extendBasis(B, p, cx, cy), cx, cy), i = 0;
+    else e = encloseBasis(B = extendBasis(B, p)), i = 0;
   }
 
   return e;
 }
 
-function extendBasis(B, p, cx, cy) {
+function extendBasis(B, p) {
   var i, j;
 
   if (enclosesWeakAll(p, B)) return [p];
@@ -48,7 +36,7 @@ function extendBasis(B, p, cx, cy) {
       if (enclosesNot(encloseBasis2(B[i], B[j]), p)
           && enclosesNot(encloseBasis2(B[i], p), B[j])
           && enclosesNot(encloseBasis2(B[j], p), B[i])
-          && enclosesWeakAll(encloseBasis3(B[i], B[j], p, cx, cy), B)) {
+          && enclosesWeakAll(encloseBasis3(B[i], B[j], p), B)) {
         return [B[i], B[j], p];
       }
     }
@@ -77,11 +65,11 @@ function enclosesWeakAll(a, B) {
   return true;
 }
 
-function encloseBasis(B, cx, cy) {
+function encloseBasis(B) {
   switch (B.length) {
     case 1: return encloseBasis1(B[0]);
     case 2: return encloseBasis2(B[0], B[1]);
-    case 3: return encloseBasis3(B[0], B[1], B[2], cx, cy);
+    case 3: return encloseBasis3(B[0], B[1], B[2]);
   }
 }
 
@@ -105,7 +93,8 @@ function encloseBasis2(a, b) {
   };
 }
 
-function encloseBasis3(a, b, c, cx, cy) {
+function encloseBasis3(a, b, c) {
+  var cx = (a.x + b.x + c.x) / 3, cy = (a.y + b.y + c.y) / 3;
   var x1 = a.x - cx, y1 = a.y - cy, r1 = a.r,
       x2 = b.x - cx, y2 = b.y - cy, r2 = b.r,
       x3 = c.x - cx, y3 = c.y - cy, r3 = c.r,

test/pack/enclose-test.js

@@ -11,7 +11,7 @@ it("packEnclose(circles) handles a tricky case", () => {
     ]),
     {
       r: 20.790781637717117,
-      x: 12.80193548387097,
+      x: 12.801935483870967,
       y: 61.59615384615385
     }
   );