Just a couple of Advent of Code puzzles solved in C. When possible I try to use non obvious ways to solve the puzzle, to make things more creative:
- Day 1 makes use of a simple streaming algorithm to retain top-N max entries.
- Day 2 turns the logic of Rock, Paper, Scissor into a simple equation modulo N.
- Day 3 makes use of bitmaps.
- Day 4 shows abstracting with C structures.
- Day 5 shows linked lists are useful.
- Day 6 will solve in
O(N)instead ofO(N*M). - Day 7 uses recursion and building ad-hoc data structures.
- Day 8 walks data structures using a velocity vector.
- Day 9 has nothing special. Just plain C code to simulate the rope.
- Day 10 Simple but fun. Nothing special. Hints at cycles-exact emulation.
- Day 11 Is an example of how you should not do parsing, assuming tons of stuff about your input. The program uses the LCM to avoid overflow. Yet I had to change int to long, and I did it brutally in
2.c, with vim search and replace. - Day 12 implements the worst queue you'll ever see.
- Day 13 uses a recursive parser that generates nested objects.
- Day 14 makes AOC a bit boring. Maybe the last I'll do? Note that here it was not needed to simulate every sand grain again, ad I did. It is possible to remember the last position of the previous sand grain before it rested and continue from there. But the execution time would not change practically, the problem is too small.
- Day 15 must show, otherwise no way to solve part 2, that it is possible to get smart when the search space is huge.
- Day 16 Worst solution so far (back home saturday night, half drunk, can't do better than that): shows how a terrible heuristic can help you brute-force the solution. Warning: the program is quite broken and works for sure only on my
input.txt, that you can find inside the directory. - Day 17 Skipped Tetris because of boredom & weekend.
- Day 18 3D flood filling with recursive flood() function.