2559. Count Vowel Strings in Ranges
## 思路
prefix sum
寫了一年的Python
今年來寫C++
## Code
```cpp
class Solution {
public:
vector<int> vowelStrings(vector<string>& words, vector<vector<int>>&
queries) {
unordered_set<char> vowels = {'a', 'e', 'i', 'o', 'u'};
vector<int> prefix = {0};
int count = 0;
for (string& word: words) {
if (vowels.count(word.front()) &&
vowels.count(word.back()))
count++;
prefix.push_back(count);
}
vector<int> res;
for (auto& q: queries) {
res.push_back(prefix[q[1]+1] - prefix[q[0]]);
}
return res;
}
};
```