Here we give a proof of Ogden's Lemma, which is a generalization of the pumping lemma for context-free languages. It's the same general idea, except now we can arbitrarily mark a number of symbols in the string, and the decomposition of the string contains some number of marked symbols. This generalizes the usual pumping lemma because the usual PL has "marked" symbols as being all of the symbols in the string. But for Ogden's Lemma, we can have some unmarked characters. Thanks to the following supporters of the channel for helping support this video. If you want to contribute, links are below. Names are listed in alphabetical order by surname. Platinum: Micah Wood Silver: Dolev Abuhazira, Simone Glinz, Timmy Gy, Josh Hibschman, Patrik Keinonen, Travis Schnider, and Tao Su Easy Theory Website: https://www.easytheory.org Become a member: https://www.youtube.com/channel/UC3VY6RTXegnoSD_q446oBdg/join Donation (appears on streams): https://streamlabs.com/easytheory1/tip Paypal: https://paypal.me/easytheory Patreon: https://www.patreon.com/easytheory Discord: https://discord.gg/SD4U3hs Merch: Language Hierarchy Apparel: https://teespring.com/language-hierarchy?pid=2&cid=2122 Pumping Lemma Apparel: https://teespring.com/pumping-lemma-for-regular-lang If you like this content, please consider subscribing to my channel: https://www.youtube.com/channel/UC3VY6RTXegnoSD_q446oBdg?sub_confirmation=1 ▶SEND ME THEORY QUESTIONS◀ ryan.e.dougherty@icloud.com ▶ABOUT ME◀ I am a professor of Computer Science, and am passionate about CS theory. I have taught many courses at several different universities, including several sections of undergraduate and graduate theory-level classes. ... https://www.youtube.com/watch?v=_95IZWDRHNQ

Here we prove that the emptiness problem for Turing Machines is undecidable via Rice's theorem; this problem is also known as the E_TM problem. This is a simple application of Rice, and all we need to do is to show that the language is a nontrivial property of TM languages. The example TMs needed are very easy and straightforward. Easy Theory Website: https://www.easytheory.org Discord: https://discord.gg/SD4U3hs If you like this content, please consider subscribing to my channel: https://www.youtube.com/channel/UC3VY6RTXegnoSD_q446oBdg?sub_confirmation=1 ▶ABOUT ME◀ I am a professor of Computer Science, and am passionate about it. I have taught many courses at several different universities, including several sections of undergraduate and graduate theory-level classes. The views expressed in this video are not reflective of any of my current or former employers. ... https://www.youtube.com/watch?v=b33N0rDhVlY

Here we introduce the notion of "logarithmic space", which is understanding what problems can be solved with a "very small" amount of space. We define what a Turing Machine needs to do in order to achieve that, as well as give some example problems that are in deterministic log space, and nondeterministic log space. What is space in complexity theory? It is the maximum amount of cells used on a Turing Machine that runs on inputs of size n. See https://www.youtube.com/watch?v=yMhQdU5j6ag&t=8s&ab_channel=EasyTheory for more details. Timeline: 0:00 - Intro 2:30 - Model for Small Space 7:30 - Definition of Log Space and Nondet Log Space 8:30 - All regular languages are in L 15:05 - {0^n 1^n} is in L 18:25 - PATH vs DPATH, DPATH in NL Easy Theory Website: https://www.easytheory.org Become a member: https://www.youtube.com/channel/UC3VY6RTXegnoSD_q446oBdg/join Donation (appears on streams): https://streamlabs.com/easytheory1/tip Paypal: https://paypal.me/easytheory Patreon: https://www.patreon.com/easytheory Discord: https://discord.gg/SD4U3hs Youtube Live Streaming (Sundays) - subscribe for when these occur. Merch: Language Hierarchy Apparel: https://teespring.com/language-hierarchy?pid=2&cid=2122 Pumping Lemma Apparel: https://teespring.com/pumping-lemma-for-regular-lang If you like this content, please consider subscribing to my channel: https://www.youtube.com/channel/UC3VY6RTXegnoSD_q446oBdg?sub_confirmation=1 ▶SEND ME THEORY QUESTIONS◀ ryan.e.dougherty@icloud.com ▶ABOUT ME◀ I am a professor of Computer Science, and am passionate about CS theory. I have taught many courses at several different universities, including several sections of undergraduate and graduate theory-level classes. ... https://www.youtube.com/watch?v=X9R6mvENyQQ

This is another jest at all complexity theory computer science professors (me included). Here we show some more memes of the complexity theory computer science class. If you want to actually learn some of the real stuff behind the memes, there are lots of playlists in my channel (including the one linked to in the card). The truth is that Computer Science (and this class, especially) is a hard major, and sometimes there is a disconnect between students and professors. This is one of the motivations behind why I'm doing what I'm doing with this channel. Thanks to the following supporters of the channel for helping support this video. If you want to contribute, links are below. Names are listed in alphabetical order by surname. Platinum: Micah Wood Silver: Dolev Abuhazira, Simone Glinz, Timmy Gy, Josh Hibschman, Patrik Keinonen, Travis Schnider, and Tao Su Easy Theory Website: https://www.easytheory.org Become a member: https://www.youtube.com/channel/UC3VY6RTXegnoSD_q446oBdg/join Donation (appears on streams): https://streamlabs.com/easytheory1/tip Paypal: https://paypal.me/easytheory Patreon: https://www.patreon.com/easytheory Discord: https://discord.gg/SD4U3hs Merch: Language Hierarchy Apparel: https://teespring.com/language-hierarchy?pid=2&cid=2122 Pumping Lemma Apparel: https://teespring.com/pumping-lemma-for-regular-lang If you like this content, please consider subscribing to my channel: https://www.youtube.com/channel/UC3VY6RTXegnoSD_q446oBdg?sub_confirmation=1 ▶SEND ME THEORY QUESTIONS◀ ryan.e.dougherty@icloud.com ▶ABOUT ME◀ I am a professor of Computer Science, and am passionate about CS theory. I have taught many courses at several different universities, including several sections of undergraduate and graduate theory-level classes. ... https://www.youtube.com/watch?v=m30xitLID-4