Excel BI - Excel Challenge 906

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excel-formulas

🔰 906 Position Swapping.xlsx says: > Swap first letter with last letter, second letter with second last letter and so on.

Published

March 24, 2026

Illustration for Excel BI - Excel Challenge 906

Challenge Description

🔰 The prompt in 906 Position Swapping.xlsx says: Swap first letter with last letter, second letter with second last letter and so on. Do the same for digits also. The goal is to: 1. identify all letter positions, 2. identify all digit positions, 3. reverse the letters among letter slots only, 4. reverse the digits among digit slots only, 5. leave everything else in place.

Solutions

library(tidyverse)
library(readxl)

path <- "Excel/900-999/906/906 Position Swapping.xlsx"
input <- read_excel(path, range = "A1:A10")
test <- read_excel(path, range = "B1:B10")

rev_mix <- function(x) {
  s <- strsplit(x, "")[[1]]
  l_pos <- str_locate_all(x, "[A-Za-z]")
  d_pos <- str_locate_all(x, "\\d")
  s[l_pos[[1]][, 1]] <- rev(s[l_pos[[1]][, 1]])
  s[d_pos[[1]][, 1]] <- rev(s[d_pos[[1]][, 1]])
  str_c(s, collapse = "")
}

result = input %>%
  mutate(Output = map_chr(String, rev_mix))

all.equal(result$Output, test$`Answer Expected`)
# [1] TRUE

Logic: Split the string into characters.; Record the positions of letters.; Record the positions of digits..
Strengths: The key is that positions are preserved by character type.
Areas for Improvement: The approach assumes the workbook structure and naming conventions stay stable, so any changed input shape would need minor adjustments.
Gem: If the string contains:

import pandas as pd
import re

path = "Excel/900-999/906/906 Position Swapping.xlsx"
input = pd.read_excel(path, usecols="A", nrows=10)
test = pd.read_excel(path, usecols="B", nrows=10)

def rev_mix(x):
    s = list(x)
    l_pos, d_pos = [m.start() for m in re.finditer(r'[A-Za-z]', x)], [m.start() for m in re.finditer(r'\d', x)]
    for pos, char in zip(l_pos, [s[i] for i in l_pos][::-1]):
        s[pos] = char
    for pos, char in zip(d_pos, [s[i] for i in d_pos][::-1]):
        s[pos] = char
    return ''.join(s)

result = input['String'].map(rev_mix)
print(result.equals(test['Answer Expected']))
# True

The Python version follows the same structure: convert the string to a mutable character list.; find all letter positions..

Difficulty Level

Easy

Once the core pattern is recognized, the implementation is short and direct.