RubyConf 2016 - Lies, Damned Lies, and Substrings by Haseeb Qureshi Generate all of the substrings of a string—a classic coding problem. But what's its time complexity? In many languages this is a pretty straightforward question, but in Ruby it turns out, it depends. Follow me into the matrix as I explore copy-on-write optimization, how substrings are created in MRI, and eventually create a custom build of Ruby to try to speed up this classic coding problem. This talk will be a mix of computer science and a deep dive into how Ruby strings work in MRI.