The Even Seesaw

A seesaw pair is PERFECT when the two weights sum to an even number. Count the perfect pairs! ⚖️

You get the weights. Print how many pairs sum to an even number. (Psst: when is a sum even? Only even+even or odd+odd…)

Example:

Input: weights = [2, 4, 3, 5] Output: 2

The evens (2, 4) form 1 pair and the odds (3, 5) form 1 pair — 1 + 1 = 2 perfect pairs.