c,c++实现单调序列问题：给定一个正整数n，求出对于n个整数集合{1,2,3,…,n-1,n}所有的排列中，单调序列的数量。-c, c++ realization of monotone sequences of problem: Given a positive integer n, find the set of the n integers {1,2,3, ..., n-1, n} all the permutations in the number of monotone sequen