added solutions

Quadtree/solutions/official solution.js

@@ -0,0 +1,71 @@
+var Quadtree = function(box) {
+  this.box = box;
+  this.point = null;
+  this.SW = null;
+  this.SE = null;
+  this.NW = null;
+  this.NE = null;
+};
+
+Quadtree.prototype.insert = function(point) {
+  if (!this.point) {
+    this.point = point;
+  } else {
+    var quadrant = this.box.findQuadrantForPoint(point);
+    if (!this[quadrant]) {
+      this[quadrant] = new Quadtree(this.box.getQuadrant(quadrant));
+    }
+    this[quadrant].insert(point);
+  }
+};
+
+Quadtree.prototype.findPointsWithin = function(searchBox) {
+  var points = [];
+  if (this.point && searchBox.contains(this.point)) {
+    points.push(this.point);
+  }
+
+  if (this.SW && searchBox.overlaps(this.SW.box)) {
+    points = points.concat(this.SW.findPointsWithin(searchBox));
+  }
+  if (this.SE && searchBox.overlaps(this.SE.box)) {
+    points = points.concat(this.SE.findPointsWithin(searchBox));
+  }
+  if (this.NW && searchBox.overlaps(this.NW.box)) {
+    points = points.concat(this.NW.findPointsWithin(searchBox));
+  }
+  if (this.NE && searchBox.overlaps(this.NE.box)) {
+    points = points.concat(this.NE.findPointsWithin(searchBox));
+  }
+
+  return points;
+};
+
+Quadtree.prototype.findNearestPointTo = function(target) {
+  if (!this.point) {
+    return null;
+  }
+
+  var xDist = 1;
+  var yDist = 1;
+
+  var searchBox = new Box(target.x - xDist, target.y - yDist, target.x + xDist, target.y + yDist);
+
+  var points = this.findPointsWithin(searchBox);
+  while (points.length === 0) {
+    searchBox.expand();
+    points = this.findPointsWithin(searchBox);
+  }
+
+  var best = null;
+  var bestDist = Infinity;
+  for (var i = 0; i < points.length; i++) {
+    var point = points[i];
+    var dist = point.distanceTo(target);
+    if (dist < bestDist) {
+      bestDist = dist;
+      best = point;
+    }
+  }
+  return best;
+};

Quadtree/spec/spec.js

@@ -146,8 +146,10 @@ describe("Quadtree tests", function() {
     });
 
     it("Works on large trees.  Properly searches 360000 points, finding 3000.", function() {
+      var startTime = Date.now();
       var points = bigFilledQuadtree.findPointsWithin(new Box(220, 280, 319, 309));
       expect(points.length).to.be(3000);
+      expect(Date.now() - startTime).to.be.below(100);
     });
   });
 
@@ -203,12 +205,14 @@ describe("Quadtree tests", function() {
     });
 
     it("Works quickly. Performs 100 queries for random points (should be under 1000 ms)", function() {
+      var startTime = Date.now();
       for (var i = 0; i < 100; i++) {
         var x = (_.random(1000, 5000))/10 - 0.05;
         var y = (_.random(1000, 5000))/10 - 0.05;
         var point = bigFilledQuadtree.findNearestPointTo(new Point(x, y));
         expectPoint(point, Math.round(x), Math.round(y));
       }
+      expect(Date.now() - startTime).to.be.below(1000);
     });
   });