Omid - Challenge 215

data-challenges
advanced-exercises
🔰 Result Question ID OFDMSD MPMXM/FS PPM/PM/ / XM
Published

March 24, 2026

Illustration for Omid - Challenge 215

Challenge Description

🔰 Result Question ID OFDMSD MPMXM/FS PPM/PM/ / XM

Solutions

library(tidyverse)
library(readxl)

path = "files/CH-215 Missing Char.xlsx"
input = read_excel(path, range = "B2:B7")
test  = read_excel(path, range = "D2:D7")

result = input %>%
  mutate(rn = row_number()) %>%
  separate_rows(ID, sep =  "") %>%
  filter(ID != "") %>%
  mutate(is_letter = str_detect(ID, "[a-zA-Z]")) %>%
  mutate(rn2 = row_number(), .by = c(rn, is_letter)) %>%
  mutate(final = ifelse(is_letter, ID, rn2)) %>%
  summarise(ID = paste(final, collapse = ""), .by = rn)

all.equal(result$ID, test$ID)
#> [1] TRUE

  • Logic:

    • Reads the workbook ranges needed for the challenge

    • Aggregates or ranks values at the relevant grouping level

    • Builds the intermediate columns that drive the final result

    • Parses the text patterns directly instead of relying on manual cleanup

  • Strengths:

    • The R solution stays close to the workbook rule and keeps the transformation compact.

  • Areas for Improvement:

    • The code assumes the sheet structure and source ranges remain stable.

  • Gem:

    • The strongest part of the solution is choosing the right intermediate representation before shaping the final output.
import pandas as pd
import re

path = "CH-215 Missing Char.xlsx"

input = pd.read_excel(path, usecols="B", skiprows=1, nrows=5)
test = pd.read_excel(path, usecols="D", skiprows=1, nrows=5).rename(columns=lambda x: re.sub(r"\.1$", "", x))

input["rn"] = range(1, len(input) + 1)
input = input.assign(ID=input["ID"].str.split("").apply(lambda x: [c for c in x if c != ""]))

def replace_non_alphanum_with_order(char_list):
    non_alpha_count = 0
    result = [
        (str(non_alpha_count := non_alpha_count + 1) if not char.isalnum() else char)
        for char in char_list
    ]
    return result

input["ID"] = input["ID"].apply(lambda x: "".join(replace_non_alphanum_with_order(x)))
input.drop(columns=["rn"], inplace=True)

print(input.equals(test)) # True

  • Logic:

    • Reads the workbook ranges needed for the challenge

    • Builds the intermediate columns that drive the final result

    • Parses the text patterns directly instead of relying on manual cleanup

    • Applies the rule iteratively until the output stabilizes

  • Strengths:

    • The Python version follows the same rule in a direct dataframe-oriented implementation.

  • Areas for Improvement:

    • The code assumes the workbook layout remains stable, so any sheet redesign would require small adjustments.

  • Gem:

    • The implementation stays close to the original workbook rule instead of adding unnecessary abstraction.

Difficulty Level

This task is moderate:

  • The core logic is clear, but the correct transformation pattern is not obvious from the raw input.

  • The challenge combines multiple reshaping, grouping, or parsing steps.