count-good-meals

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Algorithms

A good meal is a meal that contains exactly two different food items with a sum of deliciousness equal to a power of two.

You can pick any two different foods to make a good meal.

Given an array of integers <code>deliciousness</code> where <code>deliciousness[i]</code> is the deliciousness of the <code>i​​​​​​th​​​​</code>​​​​ item of food, return the number of different good meals you can make from this list modulo <code>109 + 7</code>.

Note that items with different indices are considered different even if they have the same deliciousness value.

&nbsp;
Example 1:

<pre>
Input: deliciousness = [1,3,5,7,9]
Output: 4
Explanation: The good meals are (1,3), (1,7), (3,5) and, (7,9).
Their respective sums are 4, 8, 8, and 16, all of which are powers of 2.
</pre>

Example 2:

<pre>
Input: deliciousness = [1,1,1,3,3,3,7]
Output: 15
Explanation: The good meals are (1,1) with 3 ways, (1,3) with 9 ways, and (1,7) with 3 ways.</pre>

&nbsp;
Constraints:

<ul>
	<li><code>1 &lt;= deliciousness.length &lt;= 105</code></li>
	<li><code>0 &lt;= deliciousness[i] &lt;= 220</code></li>
</ul>