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CntSortedVowelString.cpp
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54 lines (42 loc) · 1.27 KB
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/*
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
*/
/*
Code Explantion:
dp[n][k] means the number of strings constructed by at most k different characters.
If k = 1, use only u
If k = 2, use only o,u
If k = 3, use only i,o,u
If k = 4, use only e,i,o,u
If k = 5, use only a,e,i,o,u
*/
#include <bits/stdc++.h>
using namespace std;
int countVowelStrings(int n)
{
vector<vector<int>>dp(n + 1, vector<int>(6));
for (int i = 1; i <= n; ++i)
for (int k = 1; k <= 5; ++k)
dp[i][k] = dp[i][k - 1] + (i > 1 ? dp[i - 1][k] : 1);
return dp[n][5];
}
int main()
{
//cout<<"Hello World";
cout<<countVowelStrings(2);
return 0;
}