Omid - Challenge 386

data-challenges
advanced-exercises
🔰 Result Question Challenge Overview Frequency: every other day 9:00 PM (UTC) Website: and their solutions
Published

March 24, 2026

Illustration for Omid - Challenge 386

Challenge Description

🔰 Result Question Challenge Overview Frequency: every other day 9:00 PM (UTC) Website: and their solutions

Solutions

library(tidyverse)
library(readxl)

path <- "300-399/386/CH-386 Index.xlsx"
input <- read_excel(path, range = "B3:E11")
test <- read_excel(path, range = "G3:K11")

result <- input |>
  mutate(
    Index = if_else(row_number() == 1, "*", NA_character_),
    .by = c("Customer", "Product")
  )

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

  • Logic:

    • Reads the workbook ranges needed for the challenge

    • Builds the intermediate columns that drive the final result

  • 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 numpy as np
import pandas as pd

path = "300-399/386/CH-386 Index.xlsx"
input = pd.read_excel(path, usecols="B:E", skiprows=2, nrows=8)
test = pd.read_excel(path, usecols="G:K", skiprows=2, nrows=8).rename(
    columns=lambda c: __import__("re").sub(r"\.\d+$", "", c)
)

result = input.copy()
first_purchase = result.groupby(["Customer", "Product"]).cumcount() == 0
index_values = np.where(first_purchase, "*", None)
result["Index"] = pd.Series(index_values, dtype="object")

print(result.equals(test))
## Output: True

  • Logic:

    • Reads the workbook ranges needed for the challenge

    • Aggregates or ranks values at the relevant grouping level

  • 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 business rule is readable, but the workbook still requires careful implementation to reach the expected layout.