5919. 所有子字符串中的元音

https://leetcode-cn.com/problems/vowels-of-all-substrings/

思维题 若i是元音字母，则看一下组合数即可

class Solution {
    
    
public:
    long long countVowels(string w) {
    
    
        long long ans=0;
        long long  n=w.size();
        for(long long  i=0;i<n;i++)
        {
    
    
            if(w[i]=='a' || w[i]=='e' || w[i]=='i' || w[i]=='o' || w[i]=='u')
                ans=ans+(i+1)*(n-i);
        }
        return ans;
    }
};