Update erect-the-fence.py

Author: kamyu104

Python/erect-the-fence.py

@@ -14,10 +14,13 @@ def outerTrees(self, points):
         def ccw(A, B, C):
             return (B[0]-A[0])*(C[1]-A[1]) - (B[1]-A[1])*(C[0]-A[0])
 
+        if len(points) <= 3:
+            return points
         hull = []
         points.sort()
-        for i in itertools.chain(xrange(len(points)), reversed(xrange(len(points)))):
+        for i in itertools.chain(xrange(len(points)), reversed(xrange(len(points)-1))):
             while len(hull) >= 2 and ccw(hull[-2], hull[-1], points[i]) < 0:
                 hull.pop()
             hull.append(points[i])
-        return list(set(map(tuple, hull)))
+        hull.pop()
+        return hull