Excel BI - Excel Challenge 910

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excel-formulas

🔰 910 Increasing Numbers.xlsx says: > Pick up the first digit.

Published

March 24, 2026

Illustration for Excel BI - Excel Challenge 910

Challenge Description

🔰 The prompt in 910 Increasing Numbers.xlsx says: Pick up the first digit. From the remaining string, find the shortest substring that forms a number strictly greater than the previous number. Once you use a position, you can’t reuse that. Keep finding till you exhaust the string. If the remaining digits cannot form a number larger than the previous one, discard them. > > Ex. 90212148 => 9 < 021 < 214 (last digit 8 will have to be discarded). The goal is to split the digit string into a left-to-right sequence of strictly increasing numbers, always using the shortest valid next chunk.

Solutions

library(tidyverse)
library(readxl)

path <- "Excel/900-999/910/910 Increasing Numbers.xlsx"
input <- read_excel(path, range = "A1:A11")
test <- read_excel(path, range = "B1:B11")

split_inc <- function(s) {
  n <- nchar(s)
  if (n == 0) {
    character()
  }
  pos <- 1
  prev <- substr(s, pos, pos)
  out <- prev
  pos <- pos + 1
  while (pos <= n) {
    found <- FALSE
    for (len in 1:(n - pos + 1)) {
      cand <- substr(s, pos, pos + len - 1)
      if (as.integer(cand) > as.integer(prev)) {
        out <- c(out, cand)
        prev <- cand
        pos <- pos + len
        found <- TRUE
        break
      }
    }
    if (!found) break
  }
  paste(out, collapse = ", ")
}

result = input %>%
  mutate(`Answer Expected` = map_chr(`Digit Strings (Input)`, split_inc))

all.equal(result$`Answer Expected`, test$`Answer Expected`)
# > TRUE

Logic: Take the first digit as the first number.; Scan the remaining string from left to right.; Try the shortest possible next chunk first..
Strengths: The interesting part is the greedy choice: text always pick the shortest next substring that is still larger That rule is what makes the parse deterministic.
Areas for Improvement: The supplied Python file reports three mismatches, so the workbook-aligned reference here is the R logic.
Gem: text always pick the shortest next substring that is still larger

import pandas as pd

path = "Excel/900-999/910/910 Increasing Numbers.xlsx"
input = pd.read_excel(path, usecols="A", nrows=11)
test = pd.read_excel(path, usecols="B", nrows=11)

def split_inc(s):
    i, prev, out = 1, int(s[0]), [s[0]]
    while i < len(s):
        for j in range(i + 1, len(s) + 1):
            cand = s[i:j]
            if int(cand) > prev:
                out.append(cand)
                prev, i = int(cand), j
                break
        else:
            break
    return ", ".join(out)

input['Split Numbers'] = input['Digit Strings (Input)'].astype(str).apply(split_inc)
print(input['Split Numbers'] == test['Answer Expected'])
# 3 different

The supplied Python file reports three mismatches, so the workbook-aligned reference here is the R logic.

Difficulty Level

Easy

Once the core pattern is recognized, the implementation is short and direct.