方法:使用滑动窗口
class Solution {
public int maxVowels(String s, int k) {
int n = s.length();
int sum = 0;
for(int i = 0;i<k;i++){
sum += isVowel(s.charAt(i));
}
int ans = sum;
for(int i = k;i<n;i++){
sum = sum + isVowel(s.charAt(i)) - isVowel(s.charAt(i-k));
ans = Math.max(sum,ans);
}
return ans;
}
public int isVowel(char ch){
return ch=='a'||ch=='e'||ch=='i'||ch=='o'||ch=='u'?1:0;
}
}