LeetCode - Count Sorted Vowel Strings
作者:互联网
Given an integer n, return the number of strings of length n that consist only of vowels (a, e, i, o, u) and are lexicographically sorted. A string s is lexicographically sorted if for all valid i, s[i] is the same as or comes before s[i+1] in the alphabet. Example 1: Input: n = 1 Output: 5 Explanation: The 5 sorted strings that consist of vowels only are ["a","e","i","o","u"]. Example 2: Input: n = 2 Output: 15 Explanation: The 15 sorted strings that consist of vowels only are ["aa","ae","ai","ao","au","ee","ei","eo","eu","ii","io","iu","oo","ou","uu"]. Note that "ea" is not a valid string since 'e' comes after 'a' in the alphabet. Example 3: Input: n = 33 Output: 66045 Constraints: 1 <= n <= 50
Backtracking
class Solution { int total = 0; public int countVowelStrings(int n) { helper(n, 0, 0); return total; } public void helper(int n, int currentIndex, int currentSize) { if (currentSize == n) { total++; return; } for (int i = currentIndex; i < 5; i++) { helper(n, i, ++currentSize); currentSize --; } } }
标签:Count,helper,int,++,sorted,Sorted,Input,LeetCode,currentSize 来源: https://www.cnblogs.com/incrediblechangshuo/p/14435504.html