All possible sequences of given sets of characters

Question

I have the following string:

'[ABC][abcd][XYZ]'

I want to generate all possible strings where the first character is A, B, or C, the second character is a, b, c, or d, and the third character is X, Y, or Z.

Example: AcX, BaZ, etc.

How to do this, preferably within Tidyverse?

Answer 1

First splitstr the string appropriately to get a list, then using expand.grid and paste0 with do.call .

el(strsplit('[ABC][abcd][XYZ]', '[\\[|\\]]', perl=TRUE)) |>
  {\(x) x[x != '']}() |>
  sapply(strsplit, '') |>
  do.call(what=expand.grid) |>
  do.call(what=paste0)
# [1] "AaX" "BaX" "CaX" "AbX" "BbX" "CbX" "AcX" "BcX" "CcX" "AdX" "BdX" "CdX" "AaY" "BaY" "CaY" "AbY" "BbY" "CbY" "AcY" "BcY"
# [21] "CcY" "AdY" "BdY" "CdY" "AaZ" "BaZ" "CaZ" "AbZ" "BbZ" "CbZ" "AcZ" "BcZ" "CcZ" "AdZ" "BdZ" "CdZ"

Answer 2

A stringr solution:

library(stringr)
str_extract_all(x,"(?<=\\[).+?(?=\\])", simplify = TRUE) |>
  str_split("") |>
  expand.grid() |>
  do.call(what = paste0)

# [1] "AaX" "BaX" "CaX" "AbX" "BbX" "CbX" "AcX" "BcX" "CcX" "AdX" "BdX" "CdX" "AaY" "BaY" "CaY" "AbY" "BbY" "CbY" "AcY" "BcY"
#[21] "CcY" "AdY" "BdY" "CdY" "AaZ" "BaZ" "CaZ" "AbZ" "BbZ" "CbZ" "AcZ" "BcZ" "CcZ" "AdZ" "BdZ" "CdZ"

This also works, using interaction:

library(stringr)
str_extract_all(x,"(?<=\\[).+?(?=\\])", simplify = TRUE) |>
  str_split("") |>
  interaction(sep = "") |> levels()

# [1] "AaX" "BaX" "CaX" "AbX" "BbX" "CbX" "AcX" "BcX" "CcX" "AdX" "BdX" "CdX" "AaY" "BaY" "CaY" "AbY" "BbY" "CbY" "AcY" "BcY"
#[21] "CcY" "AdY" "BdY" "CdY" "AaZ" "BaZ" "CaZ" "AbZ" "BbZ" "CbZ" "AcZ" "BcZ" "CcZ" "AdZ" "BdZ" "CdZ"