Untitled

class Solution {
public:
    int numTilePossibilities(string tiles) {
        int chCount[26] = {0};

        for (int i=0;i<tiles.size();i++) {
            chCount[tiles[i] - 'A']++;
        }

        return findNumberOfSequences(chCount);
    }

    int findNumberOfSequences(int chCount[26]) {
        int cnt = 0;

        for(int i=0;i<26;i++) {
            if(chCount[i] == 0) {
                continue;
            }

            cnt++;
            chCount[i]--;

            cnt+=findNumberOfSequences(chCount);

            chCount[i]++;
        }

        return cnt;
    }
};