leetcode-problemset/leetcode/problem/strong-password-checker.html

<p>A password is considered strong if the below conditions are all met:</p>

<ul>
	<li>It has at least <code>6</code> characters and at most <code>20</code> characters.</li>
	<li>It contains at least <strong>one lowercase</strong> letter, at least <strong>one uppercase</strong> letter, and at least <strong>one digit</strong>.</li>
	<li>It does not contain three repeating characters in a row (i.e., <code>&quot;B<u><strong>aaa</strong></u>bb0&quot;</code> is weak, but <code>&quot;B<strong><u>aa</u></strong>b<u><strong>a</strong></u>0&quot;</code> is strong).</li>
</ul>

<p>Given a string <code>password</code>, return <em>the minimum number of steps required to make <code>password</code> strong. if <code>password</code> is already strong, return <code>0</code>.</em></p>

<p>In one step, you can:</p>

<ul>
	<li>Insert one character to <code>password</code>,</li>
	<li>Delete one character from <code>password</code>, or</li>
	<li>Replace one character of <code>password</code> with another character.</li>
</ul>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<pre><strong>Input:</strong> password = "a"
<strong>Output:</strong> 5
</pre><p><strong class="example">Example 2:</strong></p>
<pre><strong>Input:</strong> password = "aA1"
<strong>Output:</strong> 3
</pre><p><strong class="example">Example 3:</strong></p>
<pre><strong>Input:</strong> password = "1337C0d3"
<strong>Output:</strong> 0
</pre>
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= password.length &lt;= 50</code></li>
	<li><code>password</code> consists of letters, digits, dot&nbsp;<code>&#39;.&#39;</code> or exclamation mark <code>&#39;!&#39;</code>.</li>
</ul>