排列组合在中学数学中具有相对的独立性，是一类思考方式较为独特的问题，它对于分析问题和解决问题的能力要求较高，解法也非常灵活，并且常与集合、几何、染色等计数问题相综合，是全国高中数学联赛中的一种常见题型．在内容上，本讲立足于课本，在重点研究相异元素排列... Permutation and combination has relatively independence in middle school mathematics. It is a unique problem of a type of thinking. It has a higher requirement for the ability to analyze problems and solve problems, and the solution is also very flexible. It often counts with collections, geometry, and coloring. The problem is integrated and is a common question in the national high school mathematics league. In terms of content, this lecture is based on textbooks and focuses on the study of dissimilar elements...