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In order to win the prize for most cookies sold, my friend Alice and I are going to merge our Girl Scout Cookies orders and enter as one unit.

Each order is represented by an "order id" (an integer).

We have our lists of orders sorted numerically already, in arrays. Write a method to merge our arrays of orders into one sorted array.

For example:

int[] myArray = new int[]{3, 4, 6, 10, 11, 15}; int[] alicesArray = new int[]{1, 5, 8, 12, 14, 19}; System.out.println(Arrays.toString(mergeArrays(myArray, alicesArray))); // prints [1, 3, 4, 5, 6, 8, 10, 11, 12, 14, 15, 19]

We can do this in time and space.

If you're running a built-in sorting method, your algorithm probably takes time for that sort.

Think about edge cases! What happens when we've merged in all of the elements from one of our arrays but we still have elements to merge in from our other array?

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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 additional space, where n is the number of items in the merged array.

The added space comes from allocating the mergedArray. There's no way to do this "in place" because neither of our input arrays are necessarily big enough to hold the merged array.

But if our inputs were linked lists, we could avoid allocating a new structure and do the merge by simply adjusting the next pointers in the list nodes!

In our implementation above, we could avoid tracking currentIndexMerged and just compute it on the fly by adding currentIndexMine and currentIndexAlices. This would only save us one integer of space though, which is hardly anything. It's probably not worth the added code complexity.

What if we wanted to merge several sorted arrays? Write a method that takes as an input an array of sorted arrays and outputs a single sorted array with all the items from each array.

Do we absolutely have to allocate a new array to use for the merged output? Where else could we store our merged array? How would our method need to change?

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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