DataWeave programming challenge #8: Sum all digits to get a 1-digit number

Reader notes

Helpful comments preserved from the original post.

• Nicky van Steensel van der Aa · Jul 18, 2023

  %dw 2.0
  output application/json
  fun solve(x) =
   if (sizeOf(x)==1) x
   else solve((x reduce ((item, accumulator ) -> accumulator + item)))
  ---
  solve(payload splitBy('\n'))

• sai teja nallamallli · Jul 12, 2023

  %dw 2.0
  output application/json
  fun singleit(L:Array):Number=singleit(sum(L map singleit($ as Number default $)))
  fun singleit(X:Null):Number =0
  fun singleit(N: Number):Number = if (N==0) 0 else do{var res = (N mod 9)
  
  ---
  if(res==0) 9 else res}
  
  fun singleit(Str :Any) : Number =0
  ---
  singleit(payload splitBy "\n")

• T. sc. · Jul 12, 2023

  %dw 2.0
  output application/json
  import lines from dw::core::Strings
  fun reduceToOneDigit(inputValue) = inputValue  match {
      case d if(d is Number and sizeOf(d) == 1) -> d
      else -> reduceToOneDigit($ reduce $$ + $)
  }
  ---
  reduceToOneDigit(lines(payload))

• Diksha Dhanuka · Jul 12, 2023

  %dw 2.0
  output application/json
  
  
  ---
  payload splitBy ("\n") reduce ($+$$) reduce ($+$$) reduce($+$$)

• armandomejiam · Jul 12, 2023

  https://gist.github.com/armandomejiam/f49ea694e09f91bf6f0530920876186b

• Nirmala Vairaganthan · Jul 11, 2023

  %dw 2.0
  output application/json
  fun add(num) = if (sizeOf(num) > 1) add(sum(num splitBy "")) else num
  ---
  add(sum(payload splitBy "\n"))

• Sudiptaa · Jul 11, 2023

  %dw 2.0
  output application/json
  import * from dw::core::Strings
  
  fun sumOfDigits(n) = if(sizeOf(n) == 1) n else sumOfDigits(n reduce($ + $$))
  ---
  
  sumOfDigits(sum(lines(payload) map ($))  splitBy  "")

• Victor Manuel Rodriguez · Jul 11, 2023

  %dw 2.0
  fun sumDigits(val) = using(result = sumValue(val)) if(result / 10 >= 1)
  sumDigits("$(result)") else result
  
  fun sumValue(val) = val reduce((item, acc = 0) -> (item as Number) + acc)
  output application/json
  ---
  sumDigits(sumValue((read(payload, "text/plain") splitBy('\n'))))

FAQs

Frequently asked questions about this post.

• What does this DataWeave challenge ask you to do?

  It asks you to create a DataWeave script that sums all the digits from the input payload until only one digit is left. For example, 123 + 456 = 579, then 579 breaks down into 5 + 7 + 9 = 21, then 21 breaks down into 2 + 1 = 3, and the final result is 3 because it is a 1-digit number.

• What is the expected output for the sample input?

  For the sample input payload shown in the post (which can be in txt format), the expected output is the single digit 2.

• What clues does the post give if I'm stuck?

  The post offers three clues: first, you can sum each line from the input payload to end up with just one number; then use sizeOf() to get the length of a String; and finally you can use reduce() to sum some of the digits.

• What's the difference between the two provided solutions?

  Both solutions use the same recursive sumNums function, but Solution #1 starts from sum(lines(payload)) to total the lines first, while Solution #2 instead does payload replace "\n" with "" and then pipes that into sumNums($) as Number.

• Where should I look for help while solving this challenge?

  The post recommends referring to the DataWeave documentation only, at https://docs.mulesoft.com/dataweave/latest/ , and trying to avoid using Google or asking others so you can learn on your own and become a DataWeave expert. You can also solve it on the DataWeave Playground.

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