compute-alternating-sum

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Algorithms

You are given an integer array <code>nums</code>.

The alternating sum of <code>nums</code> is the value obtained by adding elements at even indices and subtracting elements at odd indices. That is, <code>nums[0] - nums[1] + nums[2] - nums[3]...</code>

Return an integer denoting the alternating sum of <code>nums</code>.

&nbsp;
Example 1:

<div class="example-block">
Input: nums = [1,3,5,7]

Output: -4

Explanation:

<ul>
	<li>Elements at even indices are <code>nums[0] = 1</code> and <code>nums[2] = 5</code> because 0 and 2 are even numbers.</li>
	<li>Elements at odd indices are <code>nums[1] = 3</code> and <code>nums[3] = 7</code> because 1 and 3 are odd numbers.</li>
	<li>The alternating sum is <code>nums[0] - nums[1] + nums[2] - nums[3] = 1 - 3 + 5 - 7 = -4</code>.</li>
</ul>
</div>

Example 2:

<div class="example-block">
Input: nums = [100]

Output: 100

Explanation:

<ul>
	<li>The only element at even indices is <code>nums[0] = 100</code> because 0 is an even number.</li>
	<li>There are no elements on odd indices.</li>
	<li>The alternating sum is <code>nums[0] = 100</code>.</li>
</ul>
</div>

&nbsp;
Constraints:

<ul>
	<li><code>1 &lt;= nums.length &lt;= 100</code></li>
	<li><code>1 &lt;= nums[i] &lt;= 100</code></li>
</ul>