# DataWeave programming challenge #5: Reverse a phrase's words, but keep the punctuation > Reverse the order of the words in the given phrases. However, the punctuation signs stay in the same place. - **Author:** Alex Martinez - **Published:** Apr 18, 2023 - **Category:** Challenges - **Tags:** MuleSoft, DataWeave - **Source:** https://prostdev.com/post/dataweave-programming-challenge-5 --- ## Series: DataWeave Programming Challenges (Part 5 of 8) 1. [DataWeave programming challenge #1: Add numbers separated by paragraphs and get the max number](https://prostdev.com/post/dataweave-programming-challenge-1) 2. [DataWeave programming challenge #2: Rock Paper Scissors game score system](https://prostdev.com/post/dataweave-programming-challenge-2) 3. [DataWeave programming challenge #3: Count palindrome phrases using the Strings module](https://prostdev.com/post/dataweave-programming-challenge-3) 4. [DataWeave programming challenge #4: Solve the Tower of Hanoi mathematical puzzle](https://prostdev.com/post/dataweave-programming-challenge-4) 5. DataWeave programming challenge #5: Reverse a phrase's words, but keep the punctuation (this post) 6. [DataWeave programming challenge #6: Using tail-recursion to get the factorial of a number](https://prostdev.com/post/dataweave-programming-challenge-6) 7. [DataWeave programming challenge #7: Modify certain values from a JSON structure](https://prostdev.com/post/dataweave-programming-challenge-7) 8. [DataWeave programming challenge #8: Sum all digits to get a 1-digit number](https://prostdev.com/post/dataweave-programming-challenge-8) --- > [!NOTE] > This challenge is based on [Codeacademy's Reverse Words challenge](https://discuss.codecademy.com/t/challenge-reverse-words/83796) Try to solve this challenge on your own to maximize learning. We recommend you refer to the [DataWeave documentation](https://docs.mulesoft.com/dataweave/latest/) **only**. Try to avoid using Google or asking others so you can learn on your own and become a DataWeave expert! > [!PLAYGROUND] > [Solve on the Playground](https://dataweave.mulesoft.com/learn/playground?projectMethod=GHRepo&repo=alexandramartinez%2Fdataweave-challenges&path=challenges%2F5) ## Input Consider the following input payload (can be of **txt** format): ``` Hello world May the Fourth be with you Hello world! With you, be May the Fourth With you, be May the Fourth! ``` ## Explanation of the problem Create a DataWeave script that will reverse the order of each one of the words in a phrase to form a new phrase. Each phrase or sentence is separated by a new line. Each word is separated by a space. However, the punctuation signs (! and ,) will have to stay in the same place. Lower/upper cases can be kept as-is. For example: - "Hello world!" becomes "world Hello!" - "With you, be May the Fourth!" becomes "Fourth the, May be you With!" ## Expected output In this case, the expected output would be: ``` [ "world Hello", "you with be Fourth the May", "world Hello!", "Fourth the, May be you With", "Fourth the, May be you With!" ] ``` > [!NOTE] > You can keep the output as a JSON or as a text, whatever your preference is. ## Clues If you're stuck with your solution, feel free to check out some of these clues to give you ideas on how to solve it! ### Clue #1 Keep the index of each punctuation sign so you can insert it there later ### Clue #2 You can use the isAlphanumeric function from the Strings module ### Clue #3 You can use the scan function to separate each phrase in an Array of Strings ### Clue #4 You can use the joinBy function to transform from Array to String ## Answer If you haven't solved this challenge yet, we encourage you to keep trying! It's ok if it's taking longer than you thought. We all have to start somewhere ✨ Check out the clues and read the docs before giving up. You got this!! 💙 There are many ways to solve this challenge, but you can find here my solution. I'm sure you all can make it better! :) Mine is super long 😂 ### Solution #1 ```dataweave %dw 2.0 import slice from dw::core::Arrays import lines, isAlphanumeric from dw::core::Strings output application/json --- lines(payload) map ((line) -> flatten( line scan /[^\w\d\s]|[\w]*/ ) filter (!isEmpty($))) map ((words) -> do { var wordsobj = (words map { word: $, originalIndex: $$, move: isAlphanumeric($) }) var reversed = (wordsobj filter ($.move))[-1 to 0] var spechars = wordsobj filter (not $.move) var endingStr = if (spechars[-1].originalIndex != null) (reversed[spechars[-1].originalIndex to -1].word default [] joinBy " ") else "" --- if (isEmpty(spechars)) reversed.word joinBy " " else spechars map ((charobj,coidx) -> slice( reversed, if (coidx-1 >= 0) spechars[coidx-1].originalIndex else 0, charobj.originalIndex ).word joinBy " " then trim("$($)$(charobj.word) $(endingStr)") ) joinBy " " }) ``` I also recorded myself coming up with the solution, but without explanations. Just some lo-fi music and a screen :) you can leave the video in the background while working! :D let me know if you find this useful. Subscribe to receive notifications as soon as new content is published ✨ --- ## Reader notes **decipherMiddleware** (Aug 16, 2023): My approach 🤓 ```dataweave %dw 2.0 import * from dw::core::Strings output application/json fun extract(text)= do { var list= words(text) var punc= list map (if(isAlphanumeric($)) "" else $[-1]) var rev= list[-1 to 0] map ((if(isAlphanumeric($)) $ else $[0 to -2]) ++ punc[$$]) --- rev joinBy(" ") } --- payload splitBy("\n") map (line,key)-> extract(line) ``` **Felix Schnabel** (Apr 18, 2023): My solution: ```dataweave %dw 2.0 output application/json import * from dw::core::Strings --- lines(payload) map ( words($) map [$, $$] reduce ((cur, acc = words($)[-1 to 0]) -> if(!isAlphanumeric(cur[0][-1])) acc update { case [cur[1]] -> $ ++ cur[0][-1] as String case [sizeOf(acc) - cur[1] - 1] -> $[0 to -2] } else acc ) joinBy " " ) ``` My first approach was wrong, I just inserted the special chars at the exact index where they were before 😂 So "a, bc" would be "b,c a" what's wrong of course **Shyam Raj Prasad** (Apr 18, 2023): My approach for this. ```dataweave %dw 2.0 output application/json import * from dw::core::Strings --- /* Expected output: [ "world Hello", "you with be Fourth the May", "world Hello!", "Fourth the, May be you With", "Fourth the, May be you With!" ] */ (payload splitBy "\n") map ( do { var y = $ splitBy " " map ($ filter isAlphanumeric($)) var x =($ splitBy " ") map if(isAlphanumeric($)) "" else $ filter !(isAlphanumeric($)) --- y [-1 to 0] map ( $ ++ x[$$] ) joinBy " " } ) ``` ↳ Reply to Shyam Raj Prasad — **Alex Martinez** (Apr 18, 2023): OH MY GOD SO EASY!!! Love it!!! ↳ Reply to Shyam Raj Prasad — **Felix Schnabel** (Apr 18, 2023): Damn, that solution is so nice. I was kinda thinking in that direction but couldn't write it down --- ## FAQs ### What does this DataWeave challenge ask you to do? You write a DataWeave script that reverses the order of the words in each phrase to form a new phrase, where phrases are separated by a new line and words are separated by a space, but the punctuation signs (`!` and `,`) stay in the same place; for example "Hello world!" becomes "world Hello!" and "With you, be May the Fourth!" becomes "Fourth the, May be you With!". Lower and upper cases can be kept as-is. ### How should the punctuation be handled when reversing the words? The punctuation signs stay in the same place rather than moving with the words, so as Clue #1 suggests you keep the index of each punctuation sign so you can insert it back there later after the words have been reversed. ### What clues does the post give if I get stuck? The post offers four clues: first, keep the index of each punctuation sign so you can insert it there later; second, you can use the `isAlphanumeric` function from the Strings module; third, you can use the `scan` function to separate each phrase into an Array of Strings; and finally you can use the `joinBy` function to transform from Array to String. ### Can I output the result as text instead of JSON? Yes, the post notes you can keep the output as a JSON or as a text, whatever your preference is. ### Where can I try solving this challenge? You can solve it on the DataWeave Playground using the linked project at https://dataweave.mulesoft.com/learn/playground?projectMethod=GHRepo&repo=alexandramartinez%2Fdataweave-challenges&path=challenges%2F5, and the post recommends referring only to the DataWeave documentation at https://docs.mulesoft.com/dataweave/latest/ rather than Google or others so you can learn on your own.