# 0299. Bulls and Cows

<https://leetcode.com/problems/bulls-and-cows>

## Description

You are playing the [**Bulls and Cows**](https://en.wikipedia.org/wiki/Bulls_and_Cows) game with your friend.

You write down a secret number and ask your friend to guess what the number is. When your friend makes a guess, you provide a hint with the following info:

* The number of "bulls", which are digits in the guess that are in the correct position.
* The number of "cows", which are digits in the guess that are in your secret number but are located in the wrong position. Specifically, the non-bull digits in the guess that could be rearranged such that they become bulls.

Given the secret number `secret` and your friend's guess `guess`, return *the hint for your friend's guess*.

The hint should be formatted as `"xAyB"`, where `x` is the number of bulls and `y` is the number of cows. Note that both `secret` and `guess` may contain duplicate digits.

**Example 1:**

```
**Input:** secret = "1807", guess = "7810"
**Output:** "1A3B"
**Explanation:** Bulls are connected with a '|' and cows are underlined:
"1807"
  |
"7810"
```

**Example 2:**

```
**Input:** secret = "1123", guess = "0111"
**Output:** "1A1B"
**Explanation:** Bulls are connected with a '|' and cows are underlined:
"1123"        "1123"
  |      or     |
"0111"        "0111"
Note that only one of the two unmatched 1s is counted as a cow since the non-bull digits can only be rearranged to allow one 1 to be a bull.
```

**Example 3:**

```
**Input:** secret = "1", guess = "0"
**Output:** "0A0B"
```

**Example 4:**

```
**Input:** secret = "1", guess = "1"
**Output:** "1A0B"
```

**Constraints:**

* `1 <= secret.length, guess.length <= 1000`
* `secret.length == guess.length`
* `secret` and `guess` consist of digits only.

## ac

```java
class Solution {
    public String getHint(String secret, String guess) {
        // edge cases

        // walk
        int[] s = new int[10];
        int[] g = new int[10];
        int bulls = 0;
        int cows = 0;

        // bulls
        for (int i = 0; i < secret.length(); i++) {
            if (secret.charAt(i) == guess.charAt(i)) {
                bulls++;
                continue;
            }
            s[secret.charAt(i) - '0']++;
            g[guess.charAt(i) - '0']++;
        }

        // cows
        for (int i = 0; i < s.length; i++) {
            cows += Math.min(s[i], g[i]);
        }

        // result
        return String.format("%dA%dB", bulls, cows);
    }
}
```