Lecture 20/65: PDAs: Pushdown Automata

[@ghty102]

I wish the videos were in HD or at least 360p. They are very useful, but hard to read in some cases.

[@MindIsLikeFullMoonInFall]

Thank you! Clear explanation. However, some texts were hard to read due to low resolution. I hope you can update them to HD versions in the future.

[@JoelMurphy77]

Hello, professor. Glad this video was up as I needed a refresher. I was in a computer ethics course with you a few years ago.

[@Da0yster]

Thank you so much for theses videos! I wish I could've found your video lectures at the beginning of this semester, they explain things way better in my opinion than my current professor at the college I attend. I will definitely be recommending them to anyone that asks in the future. Now let's just hope I can pass my final.

[@jurkoguba4126]

Best video I have found on this topic. Thank you so much for the upload!

[@electricwatches1]

Wow this was very helpful I'm studying for my exam and what my professor tried to explain in an hour I got from your video in just 20 mins, thank you!

[@InfiniteDesign91]

The content is very, very useful, and helped me a lot. Image quality is okay, readable. So thank you for uploading.

[@DoctorWarlock_]

Brilliant explanation! Thank you for taking the time to make this.

[@ertemeren]

Wish that more videos with examples from you.

[@cristihuma6122]

Thank you for the video ! I've finally understood the concept of pushdown automata and how it works ! By the way, first time when I saw you the description I thought your name was Harry Potter !!!

[@Ali-dn9tl]

You do an amazing job explaining this in such a simplistic manner! It would be great if you could post up problems and then solve them. Thanks again!

[@amirgul8573]

thank u sir, this lecture made me clear my backlog in this subject!!!!

[@turboheadcrab666]

Great video. Simply shows what PDA is.

[@tubenoidi]

Does the automaton compare the top of the stack with the input or not? What if in the last example there is 0 on input and 1 on top of the stack? 1 won't be popped?

[@NexusPau]

Hello professor, thank you a lot, you helped me with my computational models subject a lot.

[@zotillozotillo]

Great Video! thanks professor!

[@ekremney]

That language in 16:20 does not contain the word "111" eventhough it is a palindrome.

[@hhp3]

Ekrem Doğan You are correct. I should fix the example by adding the rules S-->0 and S-->1. But then I'd need to change the PDA to match. Since this is a somewhat minor flaw, I have decided not to re-do the video. But thanks for pointing it out! Next time...

[@kaasboyzz]

If you want it to work with odd length words as well, add the rules "0, e -> e" and "1, e -> e" between B and C

[@ThePositiev3x]

8:54 What happens if there are more 1s than 0s?

[@tanjimbinfaruk9145]

Then the machine dies. Because when it can''t match any 1 on top of the stack with a zero, it has no transition to take and so the string is rejected.

[@joemason31]

Example at 6:05

[@Nobodyyoucarabout]

10 points to Griffindor!

[@haroim]

I'm really sorry for all the Harry Potter comments you must get.

[@johnallen1883]

my jaw dropped

[@starllama2149]

Doesn't help that when he says "pushdown automata", it sounds like he's casting a spell.

[@PovilasZIT]

I think PDA at 16:30 is incorrect because all states states are connected with ε ? BEFORE first input symbol is read: trasition A->B pushes $ onto stack. Transition B->C does nothing but still happens because its conencted with ε. then transition C --> D happens because its connected with ε but this transition now pops the $ symbol that we pushed on the first strasition. Hence, before any symbol from the input is read the automaton pushes $ and then pops it leaving the machine broken ( C->D will never happen now because it won't encounter $ again). Am I wrong somewhere?

[@spike_021]

Need better quality. Was this recorded with a potato?

[@ThemisTheotokatos]

so when you say 0,0->ε the automaton will (when ever read a 0 from the tape) and (when it sees a 0 on top of the stack it will pop it) and end?

[@dovacody3512]

Reads a 0 from the input string, pops a 0 from the stack, and pushed nothing back onto the stack.

[@JoseGonzalez-yb7om]

Sorry, I can insert for example that my language accept double letters b than letters a for example abb, aabbbb, can I insert AA every time I read a letter a from the input string and when I read a letter b go unsaving a Letter A of the stacks, in summary I can insert in the stack two characters at a time regards

[@luisvillamarinvv]

Great video, thanks.

[@zengwanghuang2173]

You are helping me a lot with these videos, Thank you. But.. it would be great if the videos are more clear, a bit hard to focus on reading.

[@omargonalfa]

Great info !!!!

[@halo12221]

thank you

[@superjohn9700]

thanks

[@tedchirvasiu]

Authomathaaah

[@toxickremedy]

This guy's nam his so close to being so close.

[@JosephEssin]

much appreciated :)

[@alexg2890]

The way he says automat-ah is so C3PO @ Jabba the Hut

[@banaing]

$ rules, JFLAP drools!

[@asirsakin5562]

jk rowling were your childhood friend?