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You're working on a secret team solving coded transmissions.

Your team is scrambling to decipher a recent message, worried it's a plot to break into a major European National Cake Vault. The message has been mostly deciphered, but all the words are backward! Your colleagues have handed off the last step to you.

Write a function reverseWords that takes a message as an array of characters and reverses the order of the words in place.

Why an array of characters instead of a string?

The goal of this question is to practice manipulating arrays in place. Since Swift strings support unicode, a single character in a string might be multiple bytes. There's no way to get the ith character in a Swift string.

To sidestep this complexity, we'll work with arrays of characters instead, which let us quickly access characters at any offset.

For example:

var message = Array("cake pound steal"); reverseWords(&message) print(String(message)) // prints: "steal pound cake"

When writing your function, assume the message contains only letters and spaces, and all words are separated by one space.

We can do this in space. Remember, in place.

We can do this in time.

If you're swapping individual words one at a time, consider what happens when the words are different lengths. Isn't each swap time in the worst case?

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Start your free trial!

Log in or sign up with one click to get immediate access to free mock interview questions

Where do I enter my password?

Actually, we don't support password-based login. Never have. Just the OAuth methods above. Why?

  1. It's easy and quick. No "reset password" flow. No password to forget.
  2. It lets us avoid storing passwords that hackers could access and use to try to log into our users' email or bank accounts.
  3. It makes it harder for one person to share a paid Interview Cake account with multiple people.

time and space!

Hmm, the team used your function to finish deciphering the message. There definitely seems to be a heist brewing, but no specifics on where. Any ideas?

How would you handle punctuation?

Start your free trial!

Log in or sign up with one click to get immediate access to free mock interview questions

Where do I enter my password?

Actually, we don't support password-based login. Never have. Just the OAuth methods above. Why?

  1. It's easy and quick. No "reset password" flow. No password to forget.
  2. It lets us avoid storing passwords that hackers could access and use to try to log into our users' email or bank accounts.
  3. It makes it harder for one person to share a paid Interview Cake account with multiple people.

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