Omid - Challenge 381

data-challenges
advanced-exercises
🔰 Challenge 381: Filter!
Published

March 24, 2026

Illustration for Omid - Challenge 381

Challenge Description

🔰 Challenge 381: Filter!

Solutions

library(tidyverse)
library(readxl)

path <- "300-399/381/CH-381 Filter.xlsx"
input <- read_excel(path, range = "B3:B10")
test <- read_excel(path, range = "F3:F7")

is_valid = function(num) {
  digits <- str_extract_all(num, "\\d") %>% unlist() %>% as.integer()
  val = sum(abs(diff(digits %% 2))) >= 2
  return(val)
}

result <- input %>%
  mutate(is_valid = map_lgl(ID, is_valid)) %>%
  filter(is_valid)

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

  • 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 = "300-399/381/CH-381 Filter.xlsx"
input = pd.read_excel(path, usecols="B", skiprows=2, nrows=7)
test = pd.read_excel(path, usecols="F", skiprows=2, nrows=4)

def is_valid(num):
    digits = [int(d) for d in re.findall(r"\d", str(num))]
    parities = [d % 2 for d in digits]
    diffs = [abs(parities[i + 1] - parities[i]) for i in range(len(parities) - 1)]
    return sum(diffs) >= 2

result = input[input["ID"].apply(is_valid)].reset_index(drop=True)

print(result["ID"].equals(test["ID.1"]))
# [1] TRUE

  • Logic:

    • Reads the workbook ranges needed for the challenge

    • 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.