When comparing The C Programming Language (AKA: K&R) vs SoloLearn, the Slant community recommends SoloLearn for most people. In the question“What are the best resources to learn C/C++?” SoloLearn is ranked 4th while The C Programming Language (AKA: K&R) is ranked 6th.
Ranked in these QuestionsQuestion Ranking
Pro Well known classic
This book is so well known that it's affectionately called "K & R", after the authors.
It's been cited in many other books and is familiar to most, if not all, CS students.
Pro It's excerpted from the idea of its creators
This book is written by Dennis Ritchie, who was one of the main people behind the development and design of C and UNIX.
Pro Creative, challenging exercises
The challenges at the end of each chapter do a great job of requiring many of the skills learned up to that point. Completing the challenges is a great way of insuring you understand the material.
Pro Completely free
Pro Offline learning mode for mobile apps
Allows learning while disconnected from the net.
Pro Easy for beginners
Anyone can get started with this.
Pro Share and modify others' projects
Pro Browser-based code playgrounds
No software installation needed, just a modern web browser. On mobile devices though the mobile apps are highly recommended.
Pro Excellent mobile apps available
XP, levels, badges, certificates, etc.
Con Not for beginners
Assumes familiarity not only with programming concepts but some C language specifics.
Con Out of Date
Some commands and practices are out of date, so errata and googling is needed while going through the book.
Con Teaches bad style
The K&R style works for old Unix mainframe command-line programs that exit after a simple task and leave the cleanup to the OS; where input is only from trusted experts; and most functions are only called internally to the program. The environment is very different today. This style will get your server owned by hackers, or crash it due to a memory leak, etc. You will have to unlearn what you've learned from this book to use C correctly in the real world today.
Con Only the most commonly used languages are covered.
Con Limited usefulness for intermediate or experienced programmers
No advanced coding challenges. Look for those on other sites like hackerrank.