3392. Count Subarrays of Length Three With a Condition

Given an integer array nums, return the number of subarrays of length 3 such that the sum of the first and third numbers equals exactly half of the second number.

A subarray is a contiguous non-empty sequence of elements within an array.

func countSubarrays(nums []int) int {
    res := 0
    n := len(nums)
    for i := 0; i < n-2; i++ {
        if 2*nums[i]+2*nums[i+2] == nums[i+1] {
            res++
        }
    }
    return res
}