Powerful Numbers
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Excel BI’s Excel Challenge #319 — solved in R
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Defining the Puzzle:
We need to find which from given numbers are “more powerful” than others which means as follow:
List all Powerful numbers.
A powerful is number is that number which is perfectly divisible by square of all its Prime factors.
Ex. 225 — Prime factors are 3 and 5. In turn, 225 is perfectly divided by both 3*3 and 5*5.
Loading Data from Excel:
Lets start loading data and libraries:
library(tidyverse) library(primes) library(readxl) library(data.table) input = read_excel(“Powerful Numbers.xlsx”, range = “A1:A10”) test = read_excel(“Powerful Numbers.xlsx”, range = “B1:B6”)
Approach 1: Tidyverse with purrr
is_powerful = function(number) { vec_primes = prime_factors(number) count_vec = vec_primes %>% as.data.frame() %>% select(num = 1) %>% group_by(num) %>% summarise(a = n()) check = all(count_vec$a > 1) return(check) } result = input %>% mutate(is_powerful = map(Numbers, is_powerful)) %>% filter(is_powerful == TRUE) %>% select(Numbers)
Approach 2: Data.table
We will use exactly the same so today, so only method of calling it changes. So today DT version is up.
setDT(input) input[, is_powerful := sapply(Numbers, is_powerful)] result <- input[is_powerful == TRUE, .(Numbers)]
Validating Our Solutions:
identical(result$Numbers, test$`Answer Expected`) # [1] TRUE identical(test$`Answer Expected`, result$Numbers) # [1] TRUE
If you like my publications or have your own ways to solve those puzzles in R, Python or whatever tool you choose, let me know.
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Powerful Numbers was originally published in Numbers around us on Medium, where people are continuing the conversation by highlighting and responding to this story.
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