12
$\begingroup$

My attempt:

data = {{a, 3}, {b, 5}, {c, 2}};

output = Table[#[[1]], #[[2]]] & /@ data // Flatten

{a, a, a, b, b, b, b, b, c, c}

$\endgroup$
2
  • 2
    $\begingroup$ Also Splice@*ConstantArray@@@data $\endgroup$ – user1066 Jun 24 '20 at 10:52
  • 3
    $\begingroup$ Benchmark: Join @@ ConstantArray @@@ data < (Faster than) Flatten[ConstantArray @@@ data] < Splice@*ConstantArray @@@ data < Join @@ Table @@@ data < Flatten[Table @@@ data]. $\endgroup$ – SneezeFor16Min Jun 24 '20 at 14:42
20
$\begingroup$
Join @@ Table @@@ data
{a, a, a, b, b, b, b, b, c, c}

or

Join @@ ConstantArray @@@ data
{a, a, a, b, b, b, b, b, c, c}
## & @@ PadRight[{}, #2, {#}] & @@@ data
{a, a, a, b, b, b, b, b, c, c}
## & @@ PadRight[{#}, #2, "Fixed"] & @@@ data
{a, a, a, b, b, b, b, b, c, c}
$\endgroup$
1
  • 7
    $\begingroup$ Also Flatten[Table @@@ data] and Flatten[ConstantArray @@@ data] $\endgroup$ – Bob Hanlon Jun 24 '20 at 2:45

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