排列组合是当今发展很快的组合数学的最初步、最基本的知识。它不仅应用广泛,也是学习概率统计知识及进一步学习高等数学有关分支的预备知识。因思维方法独特,它也是培养和发展抽象思维能力和逻辑思维能力的好教材,故解决好排列组合问题至关 Permutations and combinations are the first step, the most basic knowledge, of today’s rapidly growing combinatorial mathematics. It is not only widely used, but also to learn the knowledge of probability and statistics and to further study the advanced knowledge of the relevant branches of mathematics. Because of its unique way of thinking, it is also a good teaching material for cultivating and developing abstract thinking ability and logical thinking ability, so it solves the problem of permutation and combination problems