fibonacci algorithms (recursive and iterative)

fibonacci-iterative.js

function fib(num) {
  if (num === 0) {
    return 0
  }

  if (num === 1 || num === 2) {
    return 1
  }

  let a = 1
  let b = 1

  for (let index = 3; index < num; index++) {
    [a,b] = [a + b, a]
  }

  return a + b
}

fibonacci-recursive.js

function fibRecursive(num) {
  if (num === 0) {
    return 0
  }
  if (num === 1 || num === 2) {
    return 1
  }

  return fibRecursive(num - 1) + fibRecursive(num - 2)
}

recursive: O(2^n)

http://stackoverflow.com/a/13440108/6307603

todo: i can replace the temporary variable with this pattern: https://files.slack.com/files-pri/T04KHD82U-F2TEYNB26/pasted_image_at_2016_10_24_10_31_am.png