1220. 统计元音字母序列的数目

https://leetcode-cn.com/problems/count-vowels-permutation/

动态规划

class Solution {
   public int countVowelPermutation(int n) {
         
        long a = 1, e = 1, i = 1, o = 1, u = 1;
        int mod = 1000000007;
        for (int x = 2; x <= n; x++) {
            
            long a_tmp = e;
            long e_tmp = (a + i) % mod;
            long i_tmp = (a + e + o + u) % mod;
            long o_tmp = (i + u) % mod;
            long u_tmp = a;
            
            a = a_tmp;
            e = e_tmp;
            i = i_tmp;
            o = o_tmp;
            u = u_tmp;
        }
        
        return (int)((a + e + i + o + u) % mod);
    }
}