First Day of Go
Day 1 of Go went as well as I could hope. The area I struggled the most in was how and when to use pointers. I ran into an issue in the first puzzle where my submarine struct wouldn’t update it’s HPos property and it was because my Move() method returned a copy of the submarine instead of a reference. I haven’t had to look up any hints yet but I’ve heard Advent of Code gets increasingly difficult. So I bought a book on algorithms to get as far as I can without outside help, if that counts. I tried something new today and recorded myself solving both puzzles using Asciinema and it was pretty cool being able to watch myself figure it out afterwards. Also if you haven’t used it before, prepare to have your mind blown. YOU CAN COPY/PASTE FROM THE VIDEO! I set idle timeouts for the recordings because I spent a lot of time going through the docs and a few Stack Overflow posts. The 1st puzzle took a few hours but the 2nd took ~15 mins.
Puzzle 1
— Day 2: Dive! —
Now, you need to figure out how to pilot this thing.
It seems like the submarine can take a series of commands like forward 1, down 2, or up 3:
forward X increases the horizontal position by X units. down X increases the depth by X units. up X decreases the depth by X units.
Note that since you’re on a submarine, down and up affect your depth, and so they have the opposite result of what you might expect.
The submarine seems to already have a planned course (your puzzle input). You should probably figure out where it’s going. For example:
forward 5 down 5 forward 8 up 3 down 8 forward 2
Your horizontal position and depth both start at 0. The steps above would then modify them as follows:
forward 5 adds 5 to your horizontal position, a total of 5. down 5 adds 5 to your depth, resulting in a value of 5. forward 8 adds 8 to your horizontal position, a total of 13. up 3 decreases your depth by 3, resulting in a value of 2. down 8 adds 8 to your depth, resulting in a value of 10. forward 2 adds 2 to your horizontal position, a total of 15.
After following these instructions, you would have a horizontal position of 15 and a depth of 10. (Multiplying these together produces 150.)
Calculate the horizontal position and depth you would have after following the planned course. What do you get if you multiply your final horizontal position by your final depth?
Puzzle 2
Based on your calculations, the planned course doesn’t seem to make any sense. You find the submarine manual and discover that the process is actually slightly more complicated.
In addition to horizontal position and depth, you’ll also need to track a third value, aim, which also starts at 0. The commands also mean something entirely different than you first thought:
down X increases your aim by X units. up X decreases your aim by X units. forward X does two things: It increases your horizontal position by X units. It increases your depth by your aim multiplied by X.
Again note that since you’re on a submarine, down and up do the opposite of what you might expect: “down” means aiming in the positive direction.
Now, the above example does something different:
forward 5 adds 5 to your horizontal position, a total of 5. Because your aim is 0, your depth does not change. down 5 adds 5 to your aim, resulting in a value of 5. forward 8 adds 8 to your horizontal position, a total of 13. Because your aim is 5, your depth increases by 85=40. up 3 decreases your aim by 3, resulting in a value of 2. down 8 adds 8 to your aim, resulting in a value of 10. forward 2 adds 2 to your horizontal position, a total of 15. Because your aim is 10, your depth increases by 210=20 to a total of 60.
After following these new instructions, you would have a horizontal position of 15 and a depth of 60. (Multiplying these produces 900.)
Using this new interpretation of the commands, calculate the horizontal position and depth you would have after following the planned course. What do you get if you multiply your final horizontal position by your final depth?
I realized the first recording was having problems with my vim colorscheme from the player on the Asciinema site so I switched to the Github Dark colorscheme by vv9k. Everything came out looking fine though once I embedded the player in Jekyll so I’m not sure what the problem was… may switch back to gruvbox though.