排列组合的应用题种类繁多、涉及面广、思考方法各异，特别是几类特殊的排列组合应用题，学生在解题时容易产生疑惑或失误。下面就几类特殊应用题提出一些解法，以供参考。一、在或不在问题排列组合中，某个元素要排在（或不排在）某个位置，这时解题的关键是如何恰当地满... There are a wide variety of application problems, a wide range of applications, and a variety of thinking methods. In particular, there are several types of special combinations of application problems. Students are prone to confusion or mistakes in solving problems. Here are some solutions for some special application problems for reference. First, in or out of the problem arrangement, an element must be ranked (or not) in a certain position. The key to solving the problem is how to fill it properly.