熟悉和掌握回溯搜索的定义和算法过程，并利用回溯算法求解N皇后问题，理解求解流程和搜索顺序。-Familiar with and master the definition and algorithm of back in the search process, and make use of backtracking algorithm to solve the N queens problem, understand the solving process and the search ord

Commonly used uation measures including Recall, Precision, F-Measure and Rand Accuracy are biased and should not be used without clear understanding of the biases, and corresponding identification of chance or base case levels of the statistic.