题目描述: 方法:倒推 class Solution(object): def countVowelPermutation(self, n): MOD = 10 ** 9 + 7 a=e=i=o=u= 1 for ZZZ in xrange(n-1): a2,e2,i2,o2,u2 = e+i+u,a+i,e+o,i,i+o a=a2 e=e2 i=i2 o=o2 u=u2 a %= MOD e %= MOD i %= MOD o %= MOD u %= MOD return (a+e+i+o+…