slight optimizations

lib/graph-mst.js

@@ -1,33 +1,35 @@
 module.exports = function span(graph) {
+  var prospects = graph.edges.slice()
   var edges = []
   var indices = [ 0 ]
-  while (indices.length < graph.nodes.length) {
+  while (prospects.length && indices.length < graph.nodes.length) {
     var shortest = null
     var target = null
+    var index = null
     for (var i = 0; i < indices.length; i++) {
-      var index = indices[i]
-      var node = graph.nodes[index]
-      for (var j = 0; j < graph.edges.length; j++) {
-        var edge = graph.edges[j]
+      var o = indices[i]
+      for (var j = 0; j < prospects.length; j++) {
+        var edge = prospects[j]
         var a = edge.endpoints[0]
         var b = edge.endpoints[1]
         var t = -1
-        if (a === index) {
+        if (a === o) {
           t = b
-        } else if (b === index) {
+        } else if (b === o) {
           t = a
         }
-        if ((t !== -1 && indices.indexOf(t) === -1)
-        && (!shortest || edge.weight < shortest.weight)
-        ) {
+        if (t === -1 || indices.indexOf(t) !== -1) continue
+        if (!shortest || edge.weight < shortest.weight) {
           shortest = edge
           target = t
+          index = j
         }
       }
     }
     if (shortest) {
       edges.push(shortest)
-      indices.unshift(target)
+      indices.push(target)
+      prospects.splice(index, 1)
     }
   }
   return {