Count Good Meals
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 deliciousness where deliciousness[i] is the deliciousness of the i^th item of food, return the number of different good meals you can make from this list modulo 10^9 + 7.
Note that items with different indices are considered different even if they have the same deliciousness value.
Example 1
Input
deliciousness = [1,3,5,7,9]Output
4The good meals are (1,3), (1,7), (3,5), and (7,9), whose sums are 4, 8, 8, and 16, all powers of 2.
Example 2
Input
deliciousness = [1,1,1,3,3,3,7]Output
15The good meals are (1,1) with 3 ways, (1,3) with 9 ways, and (1,7) with 3 ways.
Constraints
- 1 <= deliciousness.length <= 10^5
- 0 <= deliciousness[i] <= 2^20