Count Pairs That Form a Complete Day I
<p>Given an integer array <code>hours</code> representing times in <strong>hours</strong>, return an integer denoting the number of pairs <code>i</code>, <code>j</code> where <code>i &lt; j</code> and <code>hours[i] + hours[j]</code> forms a <strong>complete day</strong>.</p>

<p>A <strong>complete day</strong> is defined as a time duration that is an <strong>exact</strong> <strong>multiple</strong> of 24 hours.</p>

<p>For example, 1 day is 24 hours, 2 days is 48 hours, 3 days is 72 hours, and so on.</p>

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

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">hours = [12,12,30,24,24]</span></p>

<p><strong>Output:</strong> <span class="example-io">2</span></p>

<p><strong>Explanation:</strong></p>

<p>The pairs of indices that form a complete day are <code>(0, 1)</code> and <code>(3, 4)</code>.</p>
</div>

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

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">hours = [72,48,24,3]</span></p>

<p><strong>Output:</strong> <span class="example-io">3</span></p>

<p><strong>Explanation:</strong></p>

<p>The pairs of indices that form a complete day are <code>(0, 1)</code>, <code>(0, 2)</code>, and <code>(1, 2)</code>.</p>
</div>

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

<ul>
	<li><code>1 &lt;= hours.length &lt;= 100</code></li>
	<li><code>1 &lt;= hours[i] &lt;= 10<sup>9</sup></code></li>
</ul>
Array; Hash Table; Counting
func countCompleteDayPairs(hours []int) (ans int) {
	cnt := [24]int{}
	for _, x := range hours {
		ans += cnt[(24-x%24)%24]
		cnt[x%24]++
	}
	return
}