Given a list of integers, find the index at which the sum of the left half of the list is equal to the right half. If there is no index where this condition is satisfied return -1.

Note: the number that lies on the index is calculated to the left side of the list.

Example 1:

Input:

<pre tabindex="0" class="chroma"><code>nums = [1, 7, 3, 5, 6]
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>equivalent_index(nums) -&gt; 2
</code></pre>

In this example, the sum of the elements to the left of index 2 (1 + 7) is equal to the sum of the elements to the right of index 2 (5 + 6).

Example 2:

Input:

<pre tabindex="0" class="chroma"><code>nums = [1,3,5]
</code></pre>

Output:

<pre tabindex="0" class="chroma"><code>equivalent_index(nums) -&gt; -1
</code></pre>

In this example, there is no index where the sum of the elements to the left is equal to the sum of the elements to the right.

The task is to write a function that takes a list of integers as input and returns the index at which the sum of the integers to the left of the index is equal to the sum of the integers to the right. If no such index exists, the function should return -1.

Find the Index with Equal Left and Right Sum

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