Elevator-Distance.js

/*
  Imagine you start on the 5th floor of a building, then travel down to the 2nd floor, then back up to the 8th floor. You have travelled a total of 3 + 6 = 9 floors of distance.

  Given an array representing a series of floors you must reach by elevator, return an integer representing the total distance travelled for visiting each floor in the array in order.

  // simple examples
  elevatorDistance([5,2,8]) = 9
  elevatorDistance([1,2,3]) = 2
  elevatorDistance([7,1,7,1]) = 18

  // if two consecutive floors are the same,
  //distance travelled between them is 0
  elevatorDistance([3,3]) = 0
  Array will always contain at least 2 floors. Random tests will contain 2-20 elements in array, and floor values between 0 and 30.
*/

// Answer:

function elevatorDistance(array) {
  return array.reduce((acc, curr, i) => acc + Math.abs(curr - array[i + 1] || 0),0)
}

// BigO: O(n)