Question

1. Given a character or a string s, generate a result string with n (an integer) repeats of s
2. Given a list of characters or strings, and a list of the frequencies of their appearance (in correspondence), generate a result string with each string in the list repeated with the desired times as specified in the second list and StringJoin them together. For example, given {"a", "b", "c"} and {1,0,3}, I want to have "accc".

I of course want to have the most efficient way of doing these. Otherwise, my own way is too ugly and slow.

Thank you for your help!

Answer 1

rep[s_String, n_] := StringJoin[ConstantArray[s, n]]

then

rep["f", 3]
(*fff*)

next

chars = {"a", "b", "c"};
freqs = {1, 0, 3};

StringJoin[MapThread[rep, {chars, freqs}]]

gives “accc”