给定输入的字符串，计算根据字符串不同组合能生成的不同组合的个数

#include <iostream>
#include <map>
typedef unsigned long long ullong;
using std::string;

ullong factorial(ullong i) {
    if (i > 1) {
        return i * factorial(i - 1);
    }
    if (i == 1) {
        return 1;
    }
    if (i == 0) {
        return 0;
    }
}

ullong count(const string &s) {
    using std::map;
    map<char, ullong> repeat_nums;
    for (ullong i = 0; i < s.length(); i++) {
        repeat_nums[s[i]]++;
    }
    ullong result = factorial(s.length());
    for (auto it = repeat_nums.begin(); it != repeat_nums.end(); it++) {
        if (it->second > 1) {
            result /= factorial(it->second);
        }
    }
    return result;
}

int main() {
    std::cout << count("ABA") << std::endl;
    std::cout << count("ABCDEFGHHA") << std::endl;
    std::cout << count("AABBCC") << std::endl;
}