Advent Of Code

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Advent of Code is an annual Advent calendar of small programming puzzles for a variety of skill sets and skill levels that can be solved in any programming language you like.

AoC 2024

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🌻 - 2024 DAY 12 SOLUTIONS -🌻 (programming.dev)

submitted 6 days ago by [email protected] to c/[email protected]

24 comments fedilink hide all child comments

Day 12: Garden Groups

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[–] [email protected] 4 points 6 days ago (2 children)

C

No big trouble today, just a bit of careful debugging of my part 2 logic for which I was greatly helped by some Redditor’s testcase 🙏

Happy to have gotten it all in the single flood fill function without any extra passes.

Code

#include "common.h"

#define GZ 144
static char g[GZ][GZ];
static char seen[GZ][GZ];

static void
count(char c, int x, int y, int *area, int *perim, int *sides)
{
	if (g[y][x] != c) { (*perim)++; return; }
	if (seen[y][x]) return;

	*area += 1;
	seen[y][x] = 1;

	/* count start of top/left edges, end of bottom/right edges */
	*sides += g[y-1][x]!=c && ((g[y-1][x-1]==c) || (g[y][x-1]!=c));
	*sides += g[y+1][x]!=c && ((g[y+1][x+1]==c) || (g[y][x+1]!=c));
	*sides += g[y][x-1]!=c && ((g[y-1][x-1]==c) || (g[y-1][x]!=c));
	*sides += g[y][x+1]!=c && ((g[y+1][x+1]==c) || (g[y+1][x]!=c));

	count(c, x, y-1, area, perim, sides);
	count(c, x, y+1, area, perim, sides);
	count(c, x-1, y, area, perim, sides);
	count(c, x+1, y, area, perim, sides);
}

int
main(int argc, char **argv)
{
	int p1=0,p2=0, x,y, area, perim, sides;

	if (argc > 1)
		DISCARD(freopen(argv[1], "r", stdin));

	for (y=1; fgets(g[y]+1, GZ-2, stdin); y++)
		assert(y+1 < GZ);

	for (y=1; y<GZ-1; y++)
	for (x=1; x<GZ-1; x++)
		if (isalpha(g[y][x]) && !seen[y][x]) {
			area  = perim = sides = 0;
			count(g[y][x], x, y, &area, &perim, &sides);
			p1 += area * perim;
			p2 += area * sides;
		}

	printf("12: %d %d\n", p1, p2);
}

https://github.com/sjmulder/aoc/blob/master/2024/c/day12.c

[–] some_random_nick 3 points 6 days ago

Clean and concise. Admirable!

[–] [email protected] 2 points 5 days ago

Woah! That solution is a work of art!