Their point is that this is wrong. They're saying there's a few underlying principles that apply to most of these, and those are what you have to internalize.
Yeah, a few concepts like hashing, "divide and conquer" and dynamic programming is enough to solve most problems. If you understand and know how to use those and a few more well you easily ace interview questions because those are the building blocks for almost all useful simple algorithms that you get asked about in interviews.
