3392.js

/** ------------------------------------------------------------------------------
 * 
 * 3392. Count Subarrays of Length Three With a Condition
 * Topics: Array
 * https://leetcode.com/problems/count-subarrays-of-length-three-with-a-condition/description/?envType=daily-question&envId=2025-04-27
 * 
 ------------------------------------------------------------------------------ */
/**
 * @param {number[]} nums
 * @return {number}
 */
var countSubarrays = function (nums) {
  let answer = 0

  for (let i = 0; i < nums.length - 2; i++) {
    if (nums[i] + nums[i + 2] === nums[i + 1] / 2) answer++
  }

  return answer
}

console.log(countSubarrays([1, 2, 1, 4, 1]))