1208. Get equal substrings within budget

//1208. Get equal substrings within budget

class Solution {
    public int equalSubstring(String s, String t, int maxCost) {
        int[] arr = new int[s.length()];
        char[] ch = s.toCharArray(), target = t.toCharArray();

        for(int i = 0; i < arr.length; i++) {
            arr[i] = Math.abs(ch[i] - target[i]);
        }
        
        int cost = 0, start = 0, end = 0, ans = 0;

        while(start < arr.length && end < arr.length) {
            cost += arr[end++];
            
            if(cost <= maxCost) {
                ans = Math.max(ans, end - start);
            }
            else {
                while(cost > maxCost) {
                    cost -= arr[start++];
                }
            }
        }
        
        return ans;
    }
}