Coding interviews are getting harder every day. A few years back, brushing up on key data structures and going through 50-75 practice questions was more than enough prep for an interview. Today, everyone has access to massive sets of coding problems, and they've gotten more difficult to account for that. The process has gotten more competitive.
When our team sat together to brainstorm on ideas to make the interview process easier for candidates, we realized quickly that one skill helped us the most when we were preparing for coding interviews: "the ability to map a new problem to an already known problem." To help candidates with that, we've come up with a list of 15 patterns for coding questions, based on similarities in the techniques needed to solve them. As a result, once you're familiar with a pattern, you'll be able to solve dozens of problems with it. The techniques taught in this course have helped developers land Google, Facebook, Amazon, and Microsoft.
Take a look at Grokking the Coding Interview: Patterns for Coding Questions for some good examples of coding question and their answers.