updated video references for all remaining specs

Author: coderigo17

_pages/2019/ap/problems/cash/cash.adoc

@@ -40,6 +40,8 @@ It turns out that this greedy approach (i.e., algorithm) is not only locally opt
 
 == Walkthrough
 
+**Note: In the past, this problem was called Greedy.**
+
 video::6w7Tws0seJk[youtube]
 
 == Usage

_pages/2019/ap/problems/fifteen/fifteen.adoc

@@ -26,9 +26,9 @@ include::../../honesty.adoc[]
 
 == Getting Ready
 
-Have a more in-depth look at debugging techniques from Dan. (Odds are these 23 minutes with Dan will save you hours over the course of the term, since GDB is a far better tool than `printf` in many cases!)
+Have a more in-depth look at debugging techniques from Doug. (Odds are these 30 minutes with Doug will save you hours over the course of the term!)
 
-video::-G_klBQLgdc[youtube]
+video::-VtkMZjvvKaU[youtube]
 
 == Getting Started
 

_pages/2019/ap/problems/friends/friends.adoc

@@ -93,9 +93,9 @@ fahrenheit.c  hello.c  pennies.c
 
 How nice to see them again!
 
-Lastly, have a look at Christopher's short video on command-line arguments. Since we'll be converting all three of the programs listed above to accept command-line arguments (none of them currently do!), this video should come in handy.
+Lastly, have a look at Doug's short video on command-line arguments. Since we'll be converting all three of the programs listed above to accept command-line arguments (none of them currently do!), this video should come in handy.
 
-video::X8PmYwnbLKM[youtube]
+video::AI6Ccfno6Pk[youtube]
 
 If you happen to see (and are confused by!) `char *` in this and other shorts, know for now that `char *` simply means `string`. But more on that soon!
 
@@ -136,7 +136,7 @@ int main(int argc, string argv[])
 
 we then have access to two special variables that we can use inside of `main`. First is `argc`, which is an integer variable that tells us how many things the user typed in at the command line, and second is `argv`, which is an array of strings representing exactly what the user typed.
 
-Knowing this, and from the information in Christopher's short, can you now modify `hello.c` so that it prints out the name provided at the command line, instead of collecting a `string` from the user after the program has started?
+Knowing this, and from the information in Doug's short, can you now modify `hello.c` so that it prints out the name provided at the command line, instead of collecting a `string` from the user after the program has started?
 
 One more wrinkle. How do you make sure the user in fact did provide you with one (and only one) additional argument, so that you can print it out? Well remember that's what our new friend `argc` can manage for us. If the user doesn't supply a command-line argument, best to terminate the program and have them try again. One way to accomplish this might be to have this near the top of our code:
 

_pages/2019/ap/problems/house/house.adoc

@@ -30,7 +30,7 @@ video::WAxH0YHdTuA[youtube]
 
 Although they've also been known to be a bit smaller than that:
 
-video::BNpiwOkKIJ8[youtube]
+video::HXs8G7Kjrd8[youtube]
 
 But perhaps there are some that do not even use electricity?
 

_pages/2019/ap/problems/vigenere/vigenere.adoc

@@ -19,19 +19,16 @@ include::../../honesty.adoc[]
 
 == Starting Shortly
 
-We'd recommend you get started by watching a few short videos; in particular, these three on functions, command-line arguments, and the Vigenère cipher. If you happen to see (and are confused by!) `char *` in these and other shorts, know for now that `char *` simply means `string`. But more on that soon!
+We'd recommend you get started by watching a couple of short videos; in particular, these two on functions and command-line arguments. If you happen to see (and are confused by!) `char *` in these and other shorts, know for now that `char *` simply means `string`. But more on that soon!
 
-video::Pi0Yf-jn7O8[youtube]
+video::n1glFqt3g38[youtube]
 
-video::X8PmYwnbLKM[youtube]
-
-video::9zASwVoshiM[youtube]
+video::AI6Ccfno6Pk[youtube]
 
 Be sure you're reasonably comfortable answering the below questions before moving too far!
 
 * What's a function?
 * Why bother writing functions when you can just copy and paste code as needed?
-* What makes Vigenère's cipher more secure than Caesar's?
 * What does `undeclared identifier` usually indicate if outputted by `make` (or, really, `clang`)?
 
 Now execute

_pages/2019/ap/problems/whodunit/whodunit.adoc

@@ -17,16 +17,20 @@ include::../../honesty.adoc[]
 
 == Getting Ready
 
-First, curl up with Jason's short on file I/O and Rob's short on structs.  Just keep in mind that Jason's short happens to focus on ASCII (i.e., text) files as opposed to binary files (like images). More on those later!
+First, curl up with Doug's shorts on file pointers and structs.
 
-video::KwvObCA04dU[youtube,playlist="EzRwP7NV0LM"]
+video::bOF-SpEAYgk[youtube]
 
-Next, join Nate on a tour of `valgrind`, a command-line tool that will help you find "memory leaks": memory that you've allocated (i.e., asked the operating system for), as with `malloc`, but not freed (i.e., given back to the operating system).
+video::N5pA7RvvQDg[youtube]
 
-video::fvTsFjDuag8[youtube]
+Next, review (from lecture) David's introduction to `valgrind`, a command-line tool that will help you find "memory leaks": memory that you've allocated (i.e., asked the operating system for), as with `malloc`, but not freed (i.e., given back to the operating system).
+
+video::ed2lnJNf7HU[youtube,start=275,end=1091]
 
 Finally, remind yourself how debug50 works if you've forgotten or not yet used! (It's worth it!)
 
+video::VtkMZjvvKaU[youtube,start=741,end=1797]
+
 [source,bash]
 ----
 debug50 ./whodunit clue.bmp verdict.bmp