Count Alternating Subarrays
<p>You are given a <span data-keyword="binary-array">binary array</span> <code>nums</code>.</p>

<p>We call a <span data-keyword="subarray-nonempty">subarray</span> <strong>alternating</strong> if <strong>no</strong> two <strong>adjacent</strong> elements in the subarray have the <strong>same</strong> value.</p>

<p>Return <em>the number of alternating subarrays in </em><code>nums</code>.</p>

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

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">nums = [0,1,1,1]</span></p>

<p><strong>Output:</strong> <span class="example-io">5</span></p>

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

<p>The following subarrays are alternating: <code>[0]</code>, <code>[1]</code>, <code>[1]</code>, <code>[1]</code>, and <code>[0,1]</code>.</p>
</div>

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

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">nums = [1,0,1,0]</span></p>

<p><strong>Output:</strong> <span class="example-io">10</span></p>

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

<p>Every subarray of the array is alternating. There are 10 possible subarrays that we can choose.</p>
</div>

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

<ul>
	<li><code>1 &lt;= nums.length &lt;= 10<sup>5</sup></code></li>
	<li><code>nums[i]</code> is either <code>0</code> or <code>1</code>.</li>
</ul>
Array; Math
function countAlternatingSubarrays(nums: number[]): number {
    let [ans, s] = [1, 1];
    for (let i = 1; i < nums.length; ++i) {
        s = nums[i] !== nums[i - 1] ? s + 1 : 1;
        ans += s;
    }
    return ans;
}
