Find products without division, but still O(n)

prods-fast-no-division.js

/* Version without division */
var findProductsNoDiv = function (arr) {
  let forw = new Array(arr.length)
  let back = new Array(arr.length)
  let res = new Array(arr.length)
  let prod = 1
  /* Go through the array forward and multiply as we go */
  for (var i=0;i<arr.length;i++) {
    forw[i] = prod
    prod *= arr[i]
  }
  /* Now backwards */
  prod = 1
  for (var i=arr.length-1;i>=0;i--) {
    back[i] = prod
    prod *= arr[i]
  }
  /* Multiply the two arrays */
  for (var i=0;i<arr.length;i++) {
    res[i] = forw[i] * back[i]
  }
  return res
}