Omid - Challenge 282

data-challenges
advanced-exercises
🔰 Challenge 282 : Unique Characters in Rows and Columns In the Question table, identify all characters that do not appear anywhere else in their row or column.
Published

March 24, 2026

Illustration for Omid - Challenge 282

Challenge Description

🔰 Challenge 282 : Unique Characters in Rows and Columns In the Question table, identify all characters that do not appear anywhere else in their row or column.

Solutions

library(tidyverse)
library(readxl)

path = "files/200-299/282/CH-282 Advanced Filtering.xlsx"
input = read_excel(path, range = "C2:E9") %>% as.matrix()
test  = read_excel(path, range = "G2:G12") %>% pull() %>% sort()

output = matrix(0, nrow = nrow(input), ncol = ncol(input))
for (i in 1:nrow(input)) {
  for (j in 1:ncol(input)) {
    if (sum(input[i, ] == input[i, j]) == 1 && sum(input[, j] == input[i, j]) == 1) {
      output[i, j] = 1
    }
  }
}
result = input[output == 1] %>% sort() %>% unique()

all(result == test)
# [1] TRUE

  • Logic:

    • Reads the workbook ranges needed for the challenge

    • Applies the rule iteratively until the output stabilizes

  • 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 numpy as np

path = "200-299/282/CH-282 Advanced Filtering.xlsx"
input_mat = pd.read_excel(path, engine='openpyxl', usecols="C:E", skiprows=2, nrows=8, header=None).values
test = sorted(pd.read_excel(path, engine='openpyxl', usecols="G", skiprows=2, nrows=11, header=None).squeeze().tolist())

output = np.zeros_like(input_mat, dtype=int)
for i in range(input_mat.shape[0]):
    for j in range(input_mat.shape[1]):
        if (np.sum(input_mat[i, :] == input_mat[i, j]) == 1 and
            np.sum(input_mat[:, j] == input_mat[i, j]) == 1):
            output[i, j] = 1

result = sorted(set(input_mat[output == 1].tolist()))

print(result == test) # True

  • Logic:

    • Reads the workbook ranges needed for the challenge

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