题1 设有编号分别为1,2,3,4,5的五人自左至右排队,规定第k个位不站编号为k的人(k=1,2,3,4,5)有多少种排法? 这是一道常见于各种复习资料的排列组合题,许多成绩较优秀的学生面对此题都一筹莫展,总认为限制条件太多而无从下手,本文将给出此题的一种有效解法,并把此题加以推广。我们先将题1推广为: 题2 设有编号分别为 Question 1 There are five people lined up from left to right with the numbers 1, 2, 3, 4, and 5, specifying that the k-th place does not stand for people with the number k (k=1, 2, 3, 4, 5) How many ways are there? This is a common combination of various review materials. Many students with better results are overwhelmed by this question. They always think that there are too many restrictions and they cannot start. This article will give this question. An effective solution, and promote this topic. Let’s first generalize question 1 to: Question 2