Replacing integers at level 1 in a list with sequences of zeros

Question

I have a list like this:

l={{2,3},1,{4,7,2,1},3,{2,2,3,3},0,{4,4,2,1},4}

and I want to replace the natural numbers outside the sublists (at level 1) with an equal number of 0s:

replace[l]=={{2,3},0,{4,7,2,1},0,0,0,{2,2,3,3},{4,4,2,1},0,0,0,0}

Answer 1

Using Replace:

l = {{2, 3}, 1, {4, 7, 2, 1}, 3, {2, 2, 3, 3}, 0, {4, 4, 2, 1}, 4}

Replace[l, i_Integer :> Sequence @@ ConstantArray[0, i], 1]

Using SequenceReplace:

SequenceReplace[l, i : {_Integer} :> Sequence @@ ConstantArray[0, i]]

Using Sow/Reap:

First@Last@
  Reap@Scan[
    If[IntegerQ[#]
      , Sow[Splice@ConstantArray[0, #]]
      (*,Sow@Splice[Table[0,#]]*)
      , Sow@#] &, l
    , {1}
    ]

Using MapAt:

MapAt[Splice[Table[0, #]] &, l
 , Position[l, i_Integer, 1]
 ]

---

Result:

{{2, 3}, 0, {4, 7, 2, 1}, 0, 0, 0, {2, 2, 3, 3}, {4, 4, 2, 1}, 0, 0, 0, 0}

Answer 2

Similar with @rhermans

If[ListQ[#], #, Splice@ConstantArray[0, #]] & /@ l

{{2, 3}, 0, {4, 7, 2, 1}, 0, 0, 0, {2, 2, 3, 3}, {4, 4, 2, 1}, 0, 0, 0, 0}

Answer 3

l /. {x : {__Integer} :> x, i_Integer :> Splice[Table[0, i]]}

{{2, 3}, 0, {4, 7, 2, 1}, 0, 0, 0, {2, 2, 3, 3}, {4, 4, 2, 1}, 0, 0, 0, 0}

ReplaceAll >> Details:

Answer 4

Another way to do this is to use SplitBy:

Join @@ (If[Length[Level[#, {-1}]] == 1, ConstantArray[0, #], #] & /@ SplitBy[l, Length])

(*{{2, 3}, 0, {4, 7, 2, 1}, 0, 0, 0, {2, 2, 3, 3}, {4, 4, 2, 1}, 0, 0, 0, 0}*)

Or using SplitBy and ReplaceAll:

Join @@ (SplitBy[l, Length] /. {{x_Integer} :> ConstantArray[0, x]})

(*{{2, 3}, 0, {4, 7, 2, 1}, 0, 0, 0, {2, 2, 3, 3}, {4, 4, 2, 1}, 0, 0, 0, 0}*)