1255. Maximum score words formed by letters

//1255. Maximum score words formed by letters

class Solution {
    public int maxScoreWords(String[] words, char[] letters, int[] score) {
        int [] frequency = new int[26];

        for(int i = 0; i < letters.length; i++) {
            frequency[letters[i] - 'a']++;
        }

        int result = backtrack(words, frequency, score, 0);

        return result;
    }

    public static int backtrack(String[] words, int[] frr, int[] score,int idx){
        if(idx == words.length) {
            return 0;
        }

        int scoreOfaWord = 0;
        int no = backtrack(words, frr, score, idx + 1);
        boolean isValid = true;

        for(int i = 0; i < words[idx].length(); i++) {
            char ch = words[idx].charAt(i);

            if(frr[ch - 'a'] <= 0) {
                isValid = false;
            }

            frr[ch - 'a']--;
            scoreOfaWord += score[ch - 'a'];
        }

        int yes = 0;

        if(isValid) {
            yes = scoreOfaWord + backtrack(words, frr, score, idx + 1);
        }

        for(int i = 0; i < words[idx].length(); i++) {
            frr[words[idx].charAt(i) - 'a']++;
        }

        return Math.max(no, yes);
    }
}