Excel BI - Excel Challenge 701

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excel-formulas

🔰 Answer Expected Swap the diagonals in 10x10 grid as shown.

Published

March 24, 2026

Illustration for Excel BI - Excel Challenge 701

Challenge Description

🔰 Answer Expected Swap the diagonals in 10x10 grid as shown.

Solutions

library(tidyverse)
library(readxl)

path = "Excel/701 Swap Diagonals.xlsx"
input = read_excel(path, range = "A2:J11", col_names = FALSE) %>% as.matrix()
test = read_excel(path, range = "L2:U11", col_names = FALSE) %>% as.matrix()

d1 = diag(input)
d2 = diag(input[, ncol(input):1])

diag(input) <- d2
diag(input[, ncol(input):1]) <- d1

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

Logic: Read the workbook ranges needed for the challenge.
Strengths: The code maps the workbook rule into a compact, reproducible pipeline.
Areas for Improvement: The solution assumes the workbook layout and selected ranges remain stable, so any structural change in the sheet would require small adjustments.
Gem: The elegant part is how little code is needed once the correct intermediate representation is chosen.

import pandas as pd
import numpy as np

path = "701 Swap Diagonals.xlsx"
input_matrix = pd.read_excel(path, sheet_name=0, usecols="A:J", skiprows=1, nrows=10, header=None).to_numpy()
test_matrix = pd.read_excel(path, sheet_name=0, usecols="L:U", skiprows=1, nrows=10, header=None).to_numpy()

def swap_diagonals(matrix):
    for i in range(len(matrix)):
        matrix[i][i], matrix[i][~i] = matrix[i][~i], matrix[i][i]
    return matrix

res_matrix = swap_diagonals(input_matrix.copy())

print(np.array_equal(res_matrix, test_matrix)) # True

The Python version keeps the algorithm explicit, which helps when the challenge depends on a greedy or iterative rule.

Difficulty Level

Easy / Medium

The business rule is clear, though the workbook still needs a few transformation steps to reach the expected output.