Leetcode 1456

It just like question ask you longest substring without repating character, it is a sliding winodw problem. you keep track of the winodw and curr max and update the res.

class Solution {
    public int maxVowels(String s, int k) {
        // sliding window 
        int left = 0, right = 0;
        int res = 0;
        int curr = 0;
        while(right < s.length()){
            char c = s.charAt(right);
            if(c == 'a' || c == 'e' || c == 'i' || c =='o' || c == 'u'){
                // vowel 
                curr ++;
            }
            
            // shrink window
            while((right - left + 1) > k){
                // it is too big 
                
                char shrink = s.charAt(left);
                if(shrink == 'a' || shrink == 'e' || shrink == 'i' || shrink =='o' || shrink == 'u'){
                // vowel 
                    curr --;
                }
                left ++;
            }
            if((right - left + 1) <= k){
                res = Math.max(res,curr);
            }
            right ++;
        }
        return res;
    }
}