此程序从国外网站收集得到，是标准的深度优先搜索算法，可实现节点遍历和检测回路的功能，详细情况请看原英文注释

我在此程序中添加了随机性，即遇到分叉时，随机选下一个节点，成为随机深度优先搜索算法-This procedure has been collected from the foreign website, the standard depth-first search algorithm, can be achieved and the detection circuit node traversal functions, see the original details of the Note　English I would like to add a random process, that is encountered in bifurcation when a randomly selected node, as a random depth-first search algorithm