When Jaehyun Park came to the U.S. to go to Stanford, he had barely spoken English before. Just four years later, he is essentially fluent.

“I studied English, but English education in Korea is mostly reading, they don’t teach you how to talk to other people,” he says. Adjusting to Stanford was difficult, particularly when he had to complete a humanities requirement.

He calls himself a computer science theorist and not a programmer, so he does a lot of work with pencil and paper, but he got his start with a computer in his mother’s office when he was five years old. Later on, he started doing a programming contest called the Korean Olympian Informatics.

“I liked math for a long time, I was very into math when I was young,” he says. “I like the core part of programming, how fast this problem can be solved or how accurately can you do this. That’s why I’m doing theory.”

Though he’s a theorist, he is still an expert at coding. In fact, his fingers fly almost unnaturally quickly over his keyboard when he types—part of the reason, perhaps, that he is also an accomplished pianist.

“People think theorists cannot code, but that’s not the case for me,” he says. “I’m pretty sure I can code faster than most people. Coding is a skill—if you practice a lot, you can get really good at it.”

At Stanford, he was on the Stanford Programming Team, which participated in contests at the local, regional, and international levels. The Stanford team won 20^th place at the ACM International Programming Contest World Finals in 2009, and 14^th place in 2010, when they were also the North America champions. Now, he coaches the team, and runs practices every Saturday for five or six hours.

On top of his aptitude for theory and coding, he built his own computer after he broke his laptop. “I was like, oh crap, I need a computer and I just broke a really powerful machine, so I’ll just build one,” he says. “It’s very powerful, it’s got tons of memory, two hard disks for more storage, and the graphics card is really awesome.”

During his freshman year summer, he interned at Facebook with the internationalization team.

His sophomore summer, he did research with CURIS, a summer research internship program in CS at Stanford, on a program that automatically figures out what a person is doing in any given video. “Basically I give 10 seconds of a short movie clip and the program answers pretty accurately, like 40% of the time, what the person is doing,” he explains. The program was written in MATLAB and has applications in airport surveillance, among other things.

Then after his junior year, he interned at imo, a start-up in Palo Alto.

Despite his stints at companies, he applied to graduate programs this year to earn a Ph.D in computer science. “I enjoyed working at Facebook and making tons of money, but I figured I can do it later,” he says. “I enjoy studying and discovering new things.”