leetcode-problemset/leetcode/problem/bulls-and-cows.html

<p>You are playing the <strong><a href="https://en.wikipedia.org/wiki/Bulls_and_Cows" target="_blank">Bulls and Cows</a></strong> game with your friend.</p>

<p>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:</p>

<ul>
	<li>The number of &quot;bulls&quot;, which are digits in the guess that are in the correct position.</li>
	<li>The number of &quot;cows&quot;, 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.</li>
</ul>

<p>Given the secret number <code>secret</code> and your friend&#39;s guess <code>guess</code>, return <em>the hint for your friend&#39;s guess</em>.</p>

<p>The hint should be formatted as <code>&quot;xAyB&quot;</code>, where <code>x</code> is the number of bulls and <code>y</code> is the number of cows. Note that both <code>secret</code> and <code>guess</code> may contain duplicate digits.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> secret = &quot;1807&quot;, guess = &quot;7810&quot;
<strong>Output:</strong> &quot;1A3B&quot;
<strong>Explanation:</strong> Bulls are connected with a &#39;|&#39; and cows are underlined:
&quot;1807&quot;
  |
&quot;<u>7</u>8<u>10</u>&quot;</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> secret = &quot;1123&quot;, guess = &quot;0111&quot;
<strong>Output:</strong> &quot;1A1B&quot;
<strong>Explanation:</strong> Bulls are connected with a &#39;|&#39; and cows are underlined:
&quot;1123&quot;        &quot;1123&quot;
  |      or     |
&quot;01<u>1</u>1&quot;        &quot;011<u>1</u>&quot;
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.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= secret.length, guess.length &lt;= 1000</code></li>
	<li><code>secret.length == guess.length</code></li>
	<li><code>secret</code> and <code>guess</code> consist of digits only.</li>
</ul>