Hi Peter, thanks a lot for doing this. I have a h1b from 2012, i worked in the us for an year using it and returned to my home country. Is it of any use to me now, can i be cap exempt or its validity has expired and I will need a new one?
Best to forget about that interview and focus on future ones. Frontend engineering doesn't mean you can ignore performance issues in your programs. Binary trees are a very useful data structure to know in general. Ordered collections in many languages' standard libraries are internally implemented as balanced binary trees. It's good to have at least a high level understanding of this data structure.
Each letter is given a weight and it's multiplied by the length of the word it's part of to get its effective weight. Sum it up for all letters and you get the final score. Here, it seems like two 10 letter words can be formed using the given 20. Hint - blackboard is one such word.
I wake up early at 4AM, make a cup of coffee for myself, play 15 min of chess and study Spanish for another 15-20 min. This routine gets me ready to do intellectually intensive work like reading a hard technical book.
Same exact thing happened to me at Microsoft during the system design interview round. Interviewer wouldn't just let me explain and kept on arguing about a relatively minor issue and wouldn't let me proceed and in the end failed me because I didn't come up with a good design. Really the whole 45 minutes were like him repeatedly stopping me and coming back to that one issue.
I noticed I spend too much time reading wikipedia articles, jumping from one to another, so I built a chrome extension to limit that browsing time to a few minutes per day.
I've been making a Django app for over a week because I wanted to learn doing web dev. I hope to finish it another 2-3 weeks. So far, it's been a intimidating and yet fantastic experience learning about django, http, html dom, js, jquery, css, bootstrap, sqlite, orm, templates and such.
To me, it looks like you're just having problems with algorithm interviews. I have a solution for you and it's much more effective than textbooks - go to websites like www.spoj.com, projecteuler.net, topcoder.com and many other similar online sites, I suggest www.spoj.com - start with the easiest ones (on most of these sites, problems are tagged by their difficulty level) and solve them - I mean code solutions to them in a language of your choice (But C, C++ and Java are popular in interviews) - these sites have online judges where you can submit your source code, have your code run against a large suite of test cases for each problem and get results back - all in a matter of seconds.
Solve 100s of these problems(start with easy ones and move into harder ones at your ease, learn new concepts and algos as you go) and try the interviews again in another 6 months. I promise, you'll improve a lot at this kind of problem solving. I've seen a number of people do this and succeed at algo interviewing game.