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Just One More Thing Before I Go

2013-06-08T18:46:31Z

For the Kindergarteners.

What is wrong with me? Can I not even visit Florida without building something?

This one is meant for a Kindergarten drama class. It's the little brother of the air cannon I built for Hairspray. Got another free tire inflation valve from the guys at Tire Kingdom, and $15 of parts from the sprinkler place down the street (wouldn't want the fittings exploding like last time), with another $15 in valve and pipe from Lowe's: the sprinkler place didn't sell pipe in less than 20-foot lengths, and they didn't have a valve that a Kindergartener could turn.

This time, Tatiana helped me build it. She is... liberal with the blue goo. Wondering about the stubby little side? We tried to start with the short connector for the cannon, but we didn't twist it correctly, so the cannon wouldn't have been levered upwards. So we made it the endcap instead, shortening the whole thing a bit.

Hey, life is all about compromise. This was a huge success, especially considering that it's going to be used by kids: they don't need such a big compression chamber. And we figured out how to use the detachable valve end to create an infinitely-adjustable cannon angle for the next time.

Of course!

My Hobby: Built-in Irony

2013-05-04T18:42:00Z

More than $40 worth

So, everyone is aware that I work for Amazon now, right? I'm coding in the Kindle division.

So what do I the first free weekend I get in Seattle? That's right, I go hit all four used bookstores in the Pike Place area and spend all my free money on books.

Still, it's a nice haul. Plus, I'll finally get to see what this "Earthsea" stuff is all about.

Holy Well-Timed Exit Strategy, Batman!

2013-04-18T14:18:05Z

Not a model

I've recently accepted a job in Seattle. There is no better time for me to move: the kids are all the correct ages to change schools along with a bunch of other new students. Sequestration hit the government simulation industry the day after I left: the project had to arrange for furloughs. (The title is what my wife said when she heard about the furloughs. She's awesome.) The housing market is starting to look up in Florida, so my house might sell easily.

My wife is staying behind with the kids to sell the house and finish out the school year. I miss them, so I've been taking a few pictures of Seattle as I walk to work.

Neatest thing? My walk takes me right past the Space Needle!

Continue reading "Holy Well-Timed Exit Strategy, Batman!"

Just One Thing Before I Go

2013-04-18T13:55:08Z

What could this be?

I resigned on Wednesday. I was scheduled to fly on Saturday. That gave me two days to relax... or to leave behind something valuable for people I love.

One of our family friends has an autistic child. He loves to swing, but they can't afford a swingset. We were going to give them ours, but it's more than ten years old, and when we tried to pull it up, we discovered that it had become one with the ground. (We'll have to figure out some way to get that down to the dump.)

But the plastic slide, two-person glider, and rings were still in good condition. All they needed was a framework to hang on. I estimated $50 in wood and offered to build it.

Continue reading "Just One Thing Before I Go"

Silent E for Sale

2013-03-20T18:47:38Z

For Sale: $5000

Would you like to buy an 'O'? Round, and neat: a nearly perfect circle, tidy and complete...

Seriously, I'm selling my EV. I'm moving, and I don't have the time to fix it up and take it with me.

The entire saga of Silent E's rise and fall are detailed on this very site. It's cost me more than $9000 to make, with around $7000 dollars of good parts in it. Not to mention a new paint job. I'm asking $5000.

More details? Sure, read on.

Continue reading "Silent E for Sale"

23rd Anniversary? PVC!

2013-03-08T21:06:23Z

Cut down to size

Beautiful model showing off the finished project

Gotta love mitre saws. Chopped the crappy fixtures off that old cannon in no time at all. Then I bought actual Schedule-40 fittings from the sprinkler shop down the straight. Cost an extra $5, but it's worth it for the safety.

Then, since it was our anniversary, Eri helped me put it all together. We used the high-pressure "blue glue" and made certain to twist at least 90 degrees as we inserted everything. We also redesigned it to use fewer fittings, which made the twisting phase a lot easier.

Working together, and being extremely careful, it took us about two hours all told. We left it in the sun, and after about 5 hours of curing, I'll try it at tonight's performance of Hairspray!

My Creation Lives! And Dies.

2013-03-07T22:31:16Z

What could it be?

What's this collection of PVC parts? Here's a hint: I used it when I played Wilbur in Hairspray. The other actors kept calling me a "real-life Wilbur".

Continue reading "My Creation Lives! And Dies."

Happy Valentine's Day

2013-02-14T05:00:00Z

Infuriating!
Your desires are not my own.
Somehow, I'm fulfilled.

Intolerable!
When I hurt you, I feel pain.
What was I thinking?

Inconceivable!
I search for twenty-three years.
I discover more.

I love you, Eri.
I strive for your happiness.
Be my valentine.

Yes, That's More Like It

2013-02-07T17:27:01Z

Why airplanes REALLY fly.

Sorry to make a whole article with little more than a link, but, really, my kids need to read this. And this seems like the easiest way to remember.

Interview Day 8: Planes and Cycles

2013-01-22T23:49:00Z

Nice break. Time to get back with it; I'm running out of time, and I'm sure there's stuff I don't remember.

I finish studying up linked lists from Programming Interviews Exposed. Everything is pretty straightforward, but this last problem gets me: you're given a linked list; either the last node points to null (the list is normal, and acyclic), or the last node points to one of the earlier nodes in the list, in which case it has no end and is cyclic. Write an algorithm to determine which.

I progressed very quickly to the obvious answer: visit each node, and check whether it points to any of the earlier nodes in the list. No extra storage required, but it's O(n^2).

The answer, it turns out, I never would have gotten by myself: visit all the nodes at different rates. Have a slow pointer advancing one node at a time, and a fast pointer advancing two nodes at a time; if the fast pointer reaches an end, you're done, and you've only visited 1.5 times the nodes, which is O(n). If the fast pointer ever reaches the slow pointer, you've discovered a cycle visiting only 3 times the nodes... which is O(n). Of course, the author made an error that could result in a null pointer exception, and might accidentally skip the slow pointer the first time around, but those were easy to identify and rectify.

The brain teaser, Crazy Guy on the Airplane from techinterview, actually hammered home a rule of problem solving.

There are 100 passengers, numbered 1 through 100, boarding an airplane with 100 seats, also numbered 1 through 100. They'll be boarding in numerical order, and they'll sit in their numbered seat if it's available; otherwise they'll sit in a random available seat.

Problem is, passenger #1 is crazy. He randomly picks a seat, regardless of whether his seat is available.

What's the probability that passenger #100 will get to sit in his own seat?

Continue reading "Interview Day 8: Planes and Cycles"

Interview Day 7: Palindrome Brain Teaser

2013-01-21T22:12:04Z

After so much coding, I decided to take it easy with a brain teaser. I liked this techinterview palindrome puzzle. October 21, 2001 was a palindromic date, when written in MMDDYYYY format. What was the latest palindromic date previous to that?

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Interview Day 6: Unflattening a Bush

2013-01-20T21:41:00Z

Oh, great. Yesterday I flattened a bush; today you want me to un-flatten it?

This is going to require a bit of recursion, I can just tell. That's fine, I love recursion.

I kept all the child pointers when I flattened the bush, so that will tell me where the children start. I'll just traverse the list, and anytime I find a child pointer, I'll disconnect the child and all its siblings, reconnecting them as the child of the parent.

Hmmm. Only one small problem: how will I know when to stop disconnecting the child? The first parent that I encounter will get the child, and the remainder of the list afterwards, as its children.

Maybe I'd better rewrite Flatten to use a different algorithm. Certainly the interviewer would have steered me toward a solution with recognizable ends. Wouldn't he?

Continue reading "Interview Day 6: Unflattening a Bush"

Interview Day 5: Flattening a Bush

2013-01-19T02:42:26Z

Yesterday I made a linked list, in Java. Yeah, that's right.

Today I'm taking on a programming problem: given a doubly-linked list (with head and tail), where any element may have a child doubly-linked list (without head and tail), flatten the structure into a doubly-linked list.

That sounds vaguely tree-like, but trees don't usually have linked siblings. It's all just parents and children. I'm calling this a bush.

Let's look at the structure.

head->A<=>D<=>E<=>F<-tail
      |           |
      B<=>C       G
                  |
                  H

Without being told where to put stuff, I could just tack it all on the tail. But I think tacking it on after its parent is more elegant, if it can be implemented in similar complexity and space. In the bush I drew, I'd like the nodes to end up in alphabetical order.

I might even be able to do this without recursion.

Continue reading "Interview Day 5: Flattening a Bush"

Interview Prep Day 4: Linked Lists

2013-01-18T11:32:31Z

I started my studying today by looking at Programming Interviews Exposed. The author indicates that linked-list problems are common in coding interviews, because they can be solved relatively quickly, but they still expose the coder's thought processes.

As a Java programmer, I don't have much use for linked lists. Java includes a LinkedList class that takes care of all the operations for me. But according to the book, I might still be asked to implement a linked list of my own and solve some linked list problems... because it will expose my thought process.

Okay, I remember linked lists from back when I was a hot-shot C programmer. (I used to think Java was a flash in a pan. With the recent security vulnerabilities, it may turn out that way after all.) I can do this. But perhaps I should pass on the brain teaser for today. The list problems can be my brain teaser.

Implement a singly-linked list. Given a doubly-linked list (with tail pointer) where each node may have a doubly-linked list (without head or tail pointers) as a child, and the children may have their own children, flatten it to a plain doubly-linked list. Now put it back.

Continue reading "Interview Prep Day 4: Linked Lists"

Interview Prep Day 3: Dynamic Programming and Pirates!

2013-01-17T11:02:00Z

Today's studying involved "Dynamic Programming" and "Backtracking", which really turned out to be different names for little tricks I've used before in recursion. I'm going to have to look at them again, just to make sure I've got it straight, in case I get asked. I don't want to look like an idiot because I don't know something's name.

Especially if I use it all the time.

Anyway. I know why you're really here: today I tried a brainteaser from techinterview about pirates. It ARRRR-ta be a lot of fun.

Five pirates have captured a booty of 100 gold pieces. As you know, pirates use a seniority system when it comes to making decisions; in this case, the most senior pirate is pirate #5 and the least senior is pirate #1 (n00b).

You also know, of course, that pirates are greedy. And bloodthirsty. What sets this group of pirates apart, though, is how intelligent they are.

By which I mean that they're really smart (not noteworthy in the opposite direction).

Their method of dividing the 100 coins will be in keeping with pirate greed, violence, and seniority. The most senior pirate will propose a division of booty. All the pirates will vote to accept or reject the proposal. If at least 50% approve, the booty is divided according to the proposal. Otherwise, the propose-er walks the plank, and the new most senior pirate makes a new proposal.

Of course, having such massive brainpower, the most senior pirate makes a proposal that is automatically accepted. What was it?

Continue reading "Interview Prep Day 3: Dynamic Programming and Pirates!"