18
submitted 11 months ago* (last edited 11 months ago) by Ategon@programming.dev to c/advent_of_code@programming.dev

Day 7: Camel Cards

Megathread guidelines

  • Keep top level comments as only solutions, if you want to say something other than a solution put it in a new post. (replies to comments can be whatever)
  • Code block support is not fully rolled out yet but likely will be in the middle of the event. Try to share solutions as both code blocks and using something such as https://topaz.github.io/paste/ , pastebin, or github (code blocks to future proof it for when 0.19 comes out and since code blocks currently function in some apps and some instances as well if they are running a 0.19 beta)

FAQ


๐Ÿ”’ Thread is locked until there's at least 100 2 star entries on the global leaderboard

๐Ÿ”“ Thread has been unlocked after around 20 mins

you are viewing a single comment's thread
view the rest of the comments
[-] sjmulder 1 points 11 months ago

C

Sorting and counting. Used qsort() with some custom comparators.

Slightly disappointed that runtime was nonzero by time's reporting, turned out my counting of cards was a little inefficient:

static int counts[256];
for (i=0; cards[i]; i++) counts[(int)cards[i]]++;
qsort(counts, 256, sizeof(*counts), cmp_int_desc);

This sorts 256 counts but we only need those for the 13 card types. This short trick solved it:

static int counts[256];
for (i=0; cards[i]; i++) counts[(int)cards[i]]++;
for (i=0; i<13; i++) counts[i] = counts[(int)"23456789TJQKA"[i]];
qsort(counts, 13, sizeof(*counts), cmp_int_desc);

GitHub link

:::spoiler Code (110 lines)

#include "common.h"

struct hand { char cards[6]; int bet, type; };

static struct hand hands[1024];
static size_t nhands;
static int cur_part=0;	/* global to get it to cmp_hand */

static int
cmp_int_desc(const void *a, const void *b)
{
	return *(int *)b - *(int *)a;
}

static int
cmp_hand(const void *a, const void *b)
{
	const struct hand *ha = a, *hb = b;
	const char *order;
	size_t i,j;

	if (ha->type != hb->type)
		return ha->type - hb->type;

	order = cur_part==0 ? "23456789TJQKA" : "J23456789TQKA";

	for (i=0; i < LEN(ha->cards); i++) {
		if (ha->cards[i] == hb->cards[i])
			continue;
		for (j=0; order[j]; j++)
			if (order[j] == ha->cards[i]) return -1; else
			if (order[j] == hb->cards[i]) return  1;
	}

	return 0;
}

static int
get_type(char *cards)
{
	static int counts[256];
	int nj=0;
	size_t i;

	memset(counts, 0, sizeof(counts));

	for (i=0; cards[i]; i++)
		counts[(int)cards[i]]++;
	if (cur_part) {
		nj = counts['J'];
		counts['J'] = 0;
	}

	/* sort only the few counts we care about */
	for (i=0; i<13; i++)
		counts[i] = counts[(int)"23456789TJQKA"[i]];

	qsort(counts, 13, sizeof(*counts), cmp_int_desc);

	if (counts[0]+nj == 5) return 6;
	if (counts[0]+nj == 4) return 5;
	if (counts[0]+nj == 3 && counts[1]    == 2) return 4;
	if (counts[0]    == 3 && counts[1]+nj == 2) return 4;
	if (counts[0]+nj == 3) return 3;
	if (counts[0]+nj == 2 && counts[1]    == 2) return 2;
	if (counts[0]    == 2 && counts[1]+nj == 2) return 2;
	if (counts[0]+nj == 2) return 1;
	return 0;
}

static int
solve(void)
{
	int score=0;
	size_t i;

	/* precompute, avoids repeatedly doing it in cmp_hand */
	for (i=0; i<nhands; i++)
		hands[i].type = get_type(hands[i].cards);

	qsort(hands, nhands, sizeof(*hands), cmp_hand);

	for (i=0; i<nhands; i++)
		score += hands[i].bet * (int)(i+1);

	return score;
}

int
main(int argc, char **argv)
{
	int p1,p2, nt;

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

	while (1) {
		assert(nhands < LEN(hands));
		nt = fscanf(stdin, " %5s %d", hands[nhands].cards,
		    &hands[nhands].bet);
		if (nt != 2) break;
		nhands++;
	}

	cur_part=0; p1 = solve();
	cur_part=1; p2 = solve();

	printf("%d %d\n", p1, p2);
	return 0;
}
this post was submitted on 07 Dec 2023
18 points (100.0% liked)

Advent Of Code

736 readers
2 users here now

An unofficial home for the advent of code community on programming.dev!

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 2023

Solution Threads

M T W T F S S
1 2 3
4 5 6 7 8 9 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25

Rules/Guidelines

Relevant Communities

Relevant Links

Credits

Icon base by Lorc under CC BY 3.0 with modifications to add a gradient

console.log('Hello World')

founded 1 year ago
MODERATORS