299.bulls-and-cows.cpp

/*
 * @lc app=leetcode id=299 lang=cpp
 *
 * [299] Bulls and Cows
 *
 * https://leetcode.com/problems/bulls-and-cows/description/
 *
 * algorithms
 * Medium (37.73%)
 * Total Accepted:    82.8K
 * Total Submissions: 219.3K
 * Testcase Example:  '"1807"\n"7810"'
 *
 * You are playing the following Bulls and Cows game with your friend: You
 * write down a number and ask your friend to guess what the number is. Each
 * time your friend makes a guess, you provide a hint that indicates how many
 * digits in said guess match your secret number exactly in both digit and
 * position (called "bulls") and how many digits match the secret number but
 * locate in the wrong position (called "cows"). Your friend will use
 * successive guesses and hints to eventually derive the secret number.
 *
 * Write a function to return a hint according to the secret number and
 * friend's guess, use A to indicate the bulls and B to indicate the cows. 
 *
 * Please note that both secret number and friend's guess may contain duplicate
 * digits.
 *
 * Example 1:
 *
 *
 * Input: secret = "1807", guess = "7810"
 *
 * Output: "1A3B"
 *
 * Explanation: 1 bull and 3 cows. The bull is 8, the cows are 0, 1 and 7.
 *
 * Example 2:
 *
 *
 * Input: secret = "1123", guess = "0111"
 *
 * Output: "1A1B"
 *
 * Explanation: The 1st 1 in friend's guess is a bull, the 2nd or 3rd 1 is a
 * cow.
 *
 * Note: You may assume that the secret number and your friend's guess only
 * contain digits, and their lengths are always equal.
 */
class Solution {
public:
    string getHint(string secret, string guess) {
        int A=0, B=0;
        int N = secret.size();
        // bool matched[N]; fill_n(matched, N, false);
        int numbers[10];
        fill_n(numbers, 10, 0);
        for(int i=0;i<N;i++){
          if(secret[i] == guess[i])
            A++;
          else{
            if(numbers[secret[i] -'0'] < 0) B++;
            if(numbers[guess[i] - '0'] > 0) B++;
            numbers[secret[i]-'0']++;
            numbers[guess[i]-'0']--;
          }
        }

        return to_string(A) + "A" + to_string(B) + "B";
    }
};