leetcode-problemset/leetcode/problem/number-of-senior-citizens.html

<p>You are given a <strong>0-indexed</strong> array of strings <code>details</code>. Each element of <code>details</code> provides information about a given passenger compressed into a string of length <code>15</code>. The system is such that:</p>

<ul>
	<li>The first ten characters consist of the phone number of passengers.</li>
	<li>The next character denotes the gender of the person.</li>
	<li>The following two characters are used to indicate the age of the person.</li>
	<li>The last two characters determine the seat allotted to that person.</li>
</ul>

<p>Return <em>the number of passengers who are <strong>strictly </strong><strong>more than 60 years old</strong>.</em></p>

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

<pre>
<strong>Input:</strong> details = [&quot;7868190130M7522&quot;,&quot;5303914400F9211&quot;,&quot;9273338290F4010&quot;]
<strong>Output:</strong> 2
<strong>Explanation:</strong> The passengers at indices 0, 1, and 2 have ages 75, 92, and 40. Thus, there are 2 people who are over 60 years old.
</pre>

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

<pre>
<strong>Input:</strong> details = [&quot;1313579440F2036&quot;,&quot;2921522980M5644&quot;]
<strong>Output:</strong> 0
<strong>Explanation:</strong> None of the passengers are older than 60.
</pre>

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

<ul>
	<li><code>1 &lt;= details.length &lt;= 100</code></li>
	<li><code>details[i].length == 15</code></li>
	<li><code>details[i] consists of digits from &#39;0&#39; to &#39;9&#39;.</code></li>
	<li><code>details[i][10] is either &#39;M&#39; or &#39;F&#39; or &#39;O&#39;.</code></li>
	<li>The phone numbers and seat numbers of the passengers are distinct.</li>
</ul>