Mergesort implementation for http://visualsort.appspot.com/

mergesort.coffee

merge = (start, len1, len2) ->
  # merge the slice [start, start+len1) with the slice [start+len1, start+len2)
  i = start; j = start+len1
  while i < j and j < start+len2
    VA.insert(j++, i) if VA.lt(j, i)
    i++

mergesort = (start, len) ->
  # sort the slice [start, start+len)
  VA.highlight([start ... start+len])
  return if len < 2
  mid = Math.round(len / 2)
  mergesort(start, mid)
  mergesort(start+mid, len-mid)
  merge(start, mid, len)

mergesort(0, VA.length)