from sequtils import newSeqWith

type
  Forrest = ref object
    parents, heights: seq[Natural]

proc newForrestv1(n: Natural): Forrest =
  var
    p = newSeqOfCap[Natural](n + 1)
    h = newSeqOfCap[Natural](n + 1)

  for i in 0 .. n:
    p[i] = i
    h[i] = 1

  return Forrest(parents: p, heights: h)

proc newForrestv2(n: Natural): Forrest =
  for i in 0 .. n:
    result.parents[i] = i
    result.heights[i] = 1

proc newForrestv3(n: Natural): Forrest =
  result = new Forrest
  for i in 0 .. n:
    result.parents[i] = i
    result.heights[i] = 1