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Excel BI’s Excel Challenge #314 — solved in R

### Defining the Puzzle:

This puzzle is searching Atbash Palindrome.

ATBASH Palindrome — In ATBASH cipher, we replace a with z, b with y, c with x…..y with b, z with a.
Find those texts which are palindrome after doing ATBASH cipher and reversing it.
Ex. AMNZ
Reversing it gives ZNMA and after applying ATBASH cipher, it becomes AMNZ which is equal to original text i.e. it is a palindrome..

```library(tidyverse)
library(stringi)
library(data.table)

input = read_excel(“Atbash Palindromes.xlsx”, range = “A1:A10”)
test = read_excel(“Atbash Palindromes.xlsx”, range = “B1:B4”)```

### Approach 1: Tidyverse with purrr

```atbash_cipher_palindrome = function(word) {
atbash_code = rev(LETTERS)
vec = str_split(word, “”)[[1]]

atbashed = map_chr(vec, function(x) {
if (x %in% LETTERS) {
index = which(LETTERS == x)
return(atbash_code[index])
} else {
return(x)
}
})

result = all(vec == rev(atbashed))
return(result)
}

result = input %>%
mutate(check = map_lgl(Text, atbash_cipher_palindrome)) %>%
filter(check == TRUE) %>%

### Approach 2: Base R

```atbash_cipher_palindrome_base <- function(word) {
atbash_code <- rev(LETTERS)
vec <- strsplit(word, ‘’)[[1]]

atbashed <- sapply(vec, function(x) {
if (x %in% LETTERS) {
index <- which(LETTERS == x)
return(atbash_code[index])
} else {
return(x)
}
})

result <- all(vec == rev(atbashed))
return(result)
}

result_base <- input[apply(input, 1, function(row) { atbash_cipher_palindrome_base(row[“Text”])
}), , drop=FALSE]```

### Approach 3: Data.table

```atbash_cipher_palindrome_dt <- function(word) {
atbash_code <- rev(LETTERS)
vec <- strsplit(word, ‘’)[[1]]

atbashed <- sapply(vec, function(x) {
if (x %in% LETTERS) {
index <- which(LETTERS == x)
return(atbash_code[index])
} else {
return(x)
}
})

result <- all(vec == rev(atbashed))
return(result)
}
setDT(input)
atbash_cipher_palindrome_dtv <- Vectorize(atbash_cipher_palindrome_dt)
result_dt <- input[atbash_cipher_palindrome_dtv(Text), .(Answer_Expected = Text)]```

### Validating Our Solutions:

```identical(result, test)
# [1] TRUE

# [1] TRUE

# [1] TRUE```

If you like my publications or have your own ways to solve those puzzles in R, Python or whatever tool you choose, let me know.

Cypher and turn around- Atbash palindrome was originally published in Numbers around us on Medium, where people are continuing the conversation by highlighting and responding to this story.