Arithmetic Puzzle Solution

class Solution {
    public boolean isSolvable(String[] words, String result) {
        Integer[] values = new Integer[26];
        Character[] characterAssigned = new Character[10];
        List<String> allWords = new ArrayList<>(Arrays.asList(words));
        allWords.add(result);
        return generateSolution(allWords, 0 , 0, values, characterAssigned);
    }

    private boolean generateSolution(List<String> words, int index , int indexInsideWord, Integer[] values, Character[] characterAssigned) {
        if(index == words.size()) {
            return isEquationSatisfied(words, values);
        }

        boolean f = false;
        String word = words.get(index);
        if(indexInsideWord < word.length()) {
            char c = word.charAt(indexInsideWord);
            if(values[c - 'A'] == null) {
                for(int i = 0; i <= 9; i++) {
                    if(characterAssigned[i] == null) {
                        values[c - 'A'] = i;
                        characterAssigned[i] = c;
                        f = generateSolution(words, index, indexInsideWord + 1, values,characterAssigned);
                        if(f == true) {
                            return true;
                        }
                        values[c - 'A'] = null;
                        characterAssigned[i] = null;
                    }
                }
            } else {
                f = generateSolution(words, index, indexInsideWord + 1, values,characterAssigned);
            }
        }
        else {
            f = generateSolution(words, index + 1, 0, values, characterAssigned);
        }
        return f;
    }

    private boolean isEquationSatisfied(List<String> words, Integer[] values) {
        int lsum = 0;
        int num;
        for(int i = 0; i < words.size() - 1; i++) {
            num = 0;
            String word = words.get(i);
            for(int j = word.length() - 1; j >= 0; j--) {
                char c = word.charAt(j);
                num = num*10 + values[c - 'A'];
            }
           lsum+=num;
        }

        String lastWord = words.get(words.size() - 1);
        num = 0;
        for(int j = lastWord.length() - 1; j >= 0; j--) {
                char c = lastWord.charAt(j);
                num = num*10 + values[c - 'A'];
        }            
        return (lsum == num);
    }
}