Oftentimes that's the first answer that the interviewer is looking for (without the attitude). But then they want to see you code a MergeSort or QuickSort up from scratch, and explain the difference between them.
Why? Because what happens when your data set exceeds available RAM? Then you can't use the stock libraries, since they're all designed for in-memory datasets. You have to rely on external sort, which is a cousin of merge sort but has fairly different properties because of the vast difference in performance between RAM and disk. Or what if you have multiple computers available to you? Do you implement a parallel external sort over the network as a library (or service), or do you rely on domain knowledge of the keys to do some sort bucketing to each computer, like a radix sort? What are the trade-offs between each one?
Software engineering is somewhat peculiar in that 95% of the time is spent gluing pre-made components together, and yet the majority of the money is made off the 5% that requires actual creativity and knowledge. Why? Because gluing components together is a commodity. You can do it, but so can every other college grad who knows how to Google StackOverflow answers on the web. The folks who make $300K+ a year at Google/Facebook or get acquihired for a mil or two a piece or found a startup that strikes it big are the ones who know how all the "standard" stuff works on the inside so they can take it apart and piece it together in new and innovative ways.
Why? Because what happens when your data set exceeds available RAM? Then you can't use the stock libraries, since they're all designed for in-memory datasets. You have to rely on external sort, which is a cousin of merge sort but has fairly different properties because of the vast difference in performance between RAM and disk. Or what if you have multiple computers available to you? Do you implement a parallel external sort over the network as a library (or service), or do you rely on domain knowledge of the keys to do some sort bucketing to each computer, like a radix sort? What are the trade-offs between each one?
Software engineering is somewhat peculiar in that 95% of the time is spent gluing pre-made components together, and yet the majority of the money is made off the 5% that requires actual creativity and knowledge. Why? Because gluing components together is a commodity. You can do it, but so can every other college grad who knows how to Google StackOverflow answers on the web. The folks who make $300K+ a year at Google/Facebook or get acquihired for a mil or two a piece or found a startup that strikes it big are the ones who know how all the "standard" stuff works on the inside so they can take it apart and piece it together in new and innovative ways.