As a data analyst, you often have to turn input data into a consistent format in order to perform further analysis. Regular expression, or regex for short, is a commonly used tool for parsing text input.

Learning regex may seem daunting at first because of its syntax. But like learning any other skill, the more you practise using regex, the more adept you will be at it. Regex Crossword is a good way to get some of that practice. We’ll go through the steps to solve two Regex Crossword puzzles below – one Beginner and one Intermediate.

## Solving a Beginner Regex Crossword

The first puzzle we’ll look at is Beatles.

- The clue for
**column 2**says the answer is either**EP**,**IP**or**EF**, so the cell in row 2 column 2 can only be either**P**or**F**. **Row 2**is any of the characters**PLEASE**, repeated one or more times. Since**F**is not an option, row 2 column 2 must be a**P**.

- Now, let’s look at the clue for
**row 1**. The answer here is either**HE**,**LL**or multiple instances of**O**, so the cell in row 1 column 2 can only be**E**,**L**or**O**. - We know from the clue for
**column 2**that the same cell can be**E**or**I**. - This narrows down row 1 column 2 to
**E**, and by extension row 1 column 1 is**H**.

- The clue for
**column 1**says the answer is any character except**SPEAK**, repeated one or more times. - Since
**row 2**is limited to the characters**PLEASE**, we can conclude that row 2 column 1 must be**L**, since it appears in**PLEASE**but not**SPEAK**.

And there goes our first Regex Crossword! The solution is aptly the name of a Beatles song.

## Solving an Intermediate Regex Crossword

Next, we’ll tackle a more difficult puzzle – Technology.

### Into the breach

- The clues are a little more involved with this puzzle.
- We’ll look at the clue for
**column 4**first. This says the answer is**N**or**A**, repeated zero or more times. However, the cells cannot be left blank (different from having a*space*in one of the cells, which is indeed legitimate with regex syntax*\s*). - So, in fact this clue is the same as saying the answer can only consist of
**N**or**A**, though we are not told in what order and how many times each letter may appear. It would be useful to combine this information with the other clues though. **Row 1**is any of the letters**RUNT**, again repeated zero or more times. From this we can deduce row 1 column 4 cannot be**A**and has to be**N**.- The clue for
**row 2**tells us the cell in row 2 column 4 is one of the characters from**HAT**. - Similarly, this leaves only
**A**for that cell when we consider that**column 4**can only contain**N**or**A**. - The clue for
**row 2**also plainly tells us that row 2 column 1 is just an**O**.

- Looking at the clue for
**column 1**, we can see that the answer has to end in either**NO**or**ON**. From this, we know that row 3 column 1 must be**N**. - What does the clue for
**row 3**tell us? There is a capture group for the first character, and this capture group (*\1*) appears again at the end. So, row 3 column 4 is also**N**. - The rest of the clue helps us fill in the whole row as
**NDON**.

### Almost there…

- Can we deduce anything else from the clue for
**column 1**? We see that row 1 column 1 is any character but**NRU**. - On the other hand,
**row 1**consists of any of the letters**RUNT**, repeated zero or more times. So, row 1 column 1 can only be**T**. - The clue for
**column 2**says the answer is pieced together from a combination of**D**,**FU**and**UF**, repeated one or more times. In short, it could be**DFU**,**DUF**,**FUD**,**UFD**or**DDD**. - We have already filled in
**D**as the last letter here, so we’re left with**FUD**,**UFD**or**DDD**. Again,**row 1**can only use the letters**RUNT**, so the answer for**column 2**must be**UFD**.

- We’re on the home stretch now! Knowing
**column 3**ends in**O**and that the entire column is made up of zero or more occurrences of**FO**,**A**and**R**, we can see that row 2 column 3 is**F**. - And cross-referencing with the clue for
**row 1**again, we know that**R**is the only possibility for row 1 column 3.

Reading across the rows, we see IT support’s favourite line:

There are many more puzzles on the Regex Crossword website, including ones created by the community. Challenge yourself and see how you go with these puzzles – and perhaps write one of your own once you feel more comfortable with regex!