function numTilePossibilities(tiles: string): number {
    const cnt: number[] = new Array(26).fill(0);
    for (const c of tiles) {
        ++cnt[c.charCodeAt(0) - "A".charCodeAt(0)];
    }
    function dfs(cnt: number[]): number {
        let res = 0;
        for (let i = 0; i < 26; ++i) {
            if (cnt[i] > 0) {
                ++res;
                --cnt[i];
                res += dfs(cnt);
                ++cnt[i];
            }
        }
        return res;
    }
    return dfs(cnt);
}
export default numTilePossibilities;