[LeetCode] Bulls and Cows

This problem seems to be easy at the first glance, especially the problem gives a too much simpler example. Make sure you understand the problem by making more examples or refering to some other material, like the Wikipedia article.

Stefan shares a very simple and elegant solution, which is rewritten below using multiset in C++.

class Solution {
public:
    string getHint(string secret, string guess) {
        int bull = 0, both = 0, n = secret.length();
        for (int i = 0; i < n; i++)
            bull += (secret[i] == guess[i]);
        for (char c = '0'; c <= '9'; c++)
            both += min(count(secret.begin(), secret.end(), c), 
                        count(guess.begin(), guess.end(), c));
        return to_string(bull) + "A" + to_string(both - bull) + "B";
    }
};