含有限制条件的排列组合问题一直是高考中的热点,也是难点,往往让人无从下手,见了就害怕.为解决这一问题,清楚地认识和理解排列组合问题,笔者下面有一首歌诀和几道例题与读者共赏. The problem of permutations and combinations with restrictive conditions has always been a hot spot in the college entrance examination. It is also a difficult point, and often people are unable to start. When they meet, they are afraid. To solve this problem, to clearly understand and understand the permutation and combination problems, the author has a song and a few below. Example questions are shared with readers.