Scheduled phone screen. I spent a month preparing for it. I did LeetCode problems, focusing on the Meta tag and starting with the highest frequency to lowest. In total, I completed about 150-170 problems.

After passing the phone screen, an on-site interview was scheduled for a month and a half later. I redid LeetCode problems several times and prepared for behavioral and system design interviews.

Phone screen:

1. Write a method to detect if a rectangle is inside another rectangle. It takes two parameters: the first one is bigger, and the second one is smaller. Both parameters are CGRect. Return a boolean.

Next question is LeetCode 408.

Onsite:

1. Write a method to take two strings of numbers with decimals. For example, "12.892347823" and "65655.62". Return the sum of these two numbers as a string. You CANNOT convert the parameters into integers. This is similar to LeetCode 415, but for decimal numbers.

2. Write an Array extension method like func remove(removeArray: [Int]). This method removes the elements in removeArray from the original array. For example, if the array has [1,3,3,4,5,1,6] and removeArray is [1, 3], the method should remove 1 and 3 from the original array, returning [4,5,6].

3. LeetCode 31.

4. LeetCode 1249.

System design:

Design an app similar to Instagram, but users swipe horizontally. The app can swipe automatically every 10 seconds if the user is doing nothing. When a user swipes to the next photo, the timer resets to zero. Also, if a friend has posted a news feed, the server can push it to your app. A new item is inserted to the front of the queue. For example, if the app has items 1,2,3,4,5, and when your friends post items 6 and 7 while you are looking at item 1, your app will display 1, 6, 7, 2, 3, 4, 5. Need to find a way for the server to push to the app (e.g., WebSocket, polling, or push notification). I chose polling. Explain your choice.