N皇后问题：拉斯维加斯算法和回溯法的结合，可以输出每次搜索的节点数（包括成功的搜索和失败的搜索），以及直到找到一个正确结点的搜索总节点数。-N Queens problem: Las Vegas, the combination of algorithm and backtracking, can output the number of nodes per search (including the failure of successful search and the search), and until you find the right node of the total number of nodes in the search.