plotkoch

代码说明：

  Koch曲线是通过图形迭代的方式产生的，其迭代规则是：对一条线段，首先将它分成三等份，然后将中间的一份替换成以此为底边的等边三角形的另外两条边。无限次迭代下去，最终形成的曲线就是Koch曲线。(Koch curve is generated by way of graphical iteration, and its iteration rule is: for a segment, it is divided into three equal parts first, and then replace the middle of a bottom side of this equilateral triangle to the other two edges. Infinite iterations continue, the final form of the curve is the Koch curve.)