K&R is woefully out of date. Gives you no info on how to do things safely and sanely. And encourages a leet style of programming that results in catastrophic edge case bugs. As you can see in comments above where naive code that iterates backwards through an array fails when the array size is 0. Worse K&R leet style buys you absolutely nothing with a optimizing compiler written in the last 30 years.
K&R is actually fairly reasonable about performance, and much less l33t than code I have seen in the wild. It is a very good introduction about the language, and although I would not ever call it "woefully out of date" I would say that it is a good idea to read more about the current state of bugs and tooling, which is not discussed because the book is a general overview of the language.
I hate guides showing me how to do things safely and sanely from the get-go. Show me how to do it. If safety and sanity are priorities for me, I’ll seek those out on my own.