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#include "aoc.h"
#include "allocator.h"
#include "util.h"
#include "hmap.h"
#include <math.h>
#include <assert.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
struct asteroid {
int x, y;
struct asteroid *next;
};
struct dir {
int dx, dy;
};
struct asteroid *asteroids;
int width, height;
bool
hmap_dir_keycmp(struct hmap_key k1, struct hmap_key k2)
{
const struct dir *d1 = k1.p, *d2 = k2.p;
return d1->dx == d2->dx && d1->dy == d2->dy;
}
uint32_t
hmap_dir_hash(struct hmap_key key)
{
const struct dir *dir = key.p;
uint32_t hash;
hash = ((uint32_t) dir->dx & 0xFFFF);
hash |= ((uint32_t) dir->dy & 0xFFFF) << 16;
return hash;
}
void
add_asteroid(int x, int y)
{
struct asteroid **iter;
for (iter = &asteroids; *iter; iter = &((*iter)->next));
*iter = malloc(sizeof(struct asteroid));
assert(*iter != NULL);
(*iter)->x = x;
(*iter)->y = y;
(*iter)->next = NULL;
}
void
asteroids_init(void)
{
char *p;
int x, y;
asteroids = NULL;
width = height = 0;
x = y = 0;
for (p = aoc.input; *p; p++) {
switch (*p) {
case '\n':
width = x;
x = 0;
height++;
y++;
break;
case '#':
add_asteroid(x, y);
case '.':
x++;
break;
}
}
assert(width != 0 && height != 0);
}
void
asteroids_deinit(void)
{
struct asteroid *iter, *next;
for (iter = asteroids; iter; iter = next) {
next = iter->next;
free(iter);
}
}
int
gcd(int a, int b)
{
int t;
while (b) {
t = b;
b = a % b;
a = t;
}
return a;
}
void
reduce_frac(struct dir *d)
{
int cd;
cd = gcd(ABS(d->dx), ABS(d->dy));
d->dx /= cd;
d->dy /= cd;
}
void
get_vis(struct hmap *hm, const struct asteroid *a1)
{
struct hmap_link *link;
const struct asteroid *a2, *tmp;
struct dir dir, odir;
void *key;
int rc;
for (a2 = asteroids; a2; a2 = a2->next) {
if (a1 == a2) continue;
dir.dx = a2->x - a1->x;
dir.dy = a2->y - a1->y;
reduce_frac(&dir);
link = hmap_get(hm, (struct hmap_key) {.p = &dir});
if (link) {
tmp = link->value.p;
odir = (struct dir) { tmp->x - a1->x, tmp->y - a1->y };
dir = (struct dir) { a2->x - a1->x, a2->y - a1->y };
if (ABS(odir.dx) + ABS(odir.dy) > ABS(dir.dx) + ABS(dir.dy))
link->value.p = a2;
} else {
key = memdup(&dir, sizeof(struct dir));
rc = hmap_add(hm, (struct hmap_key) {.p = key},
(struct hmap_val) {.p = a2});
assert(!rc);
}
}
}
float
angle(const struct asteroid *a, const struct asteroid *base)
{
if (a->x == base->x)
return a->y > base->y ? 0 : -(float) 3.1415926;
return (float) atan2(base->x - a->x, a->y - base->y);
}
void
find_base(const struct asteroid **a_out, int *vis_out)
{
struct asteroid *a1, *cand;
struct hmap_iter iter;
struct hmap dirmap;
int vis, maxvis;
hmap_init(&dirmap, 100, hmap_dir_hash, hmap_dir_keycmp,
&stdlib_strict_heap_allocator);
maxvis = 0;
cand = NULL;
for (a1 = asteroids; a1; a1 = a1->next) {
aoc_debug("Asteroid @ %i,%i => ", a1->x, a1->y);
get_vis(&dirmap, a1);
vis = 0;
for (HMAP_ITER(&dirmap, iter))
vis++;
aoc_debug("%i vis\n", vis);
if (maxvis == 0 || vis > maxvis) {
maxvis = vis;
cand = a1;
}
for (HMAP_ITER(&dirmap, iter))
free(iter.link->key._p);
hmap_clear(&dirmap);
}
assert(cand != NULL);
hmap_deinit(&dirmap);
if (vis_out) *vis_out = maxvis;
if (a_out) *a_out = cand;
}
void
part1(void)
{
const struct asteroid *a;
int vis;
asteroids_init();
find_base(&a, &vis);
aoc_debug("Best at %i,%i with %i vis\n", a->x, a->y, vis);
aoc.answer = aprintf("%i", vis);
aoc.solution = "299";
asteroids_deinit();
}
void
part2(void)
{
const struct asteroid *base, *tmp;
struct hmap_iter iter;
const struct asteroid **list;
struct hmap dirmap;
int i, k, len;
float prev;
asteroids_init();
find_base(&base, NULL);
hmap_init(&dirmap, 100, hmap_dir_hash, hmap_dir_keycmp,
&stdlib_strict_heap_allocator);
get_vis(&dirmap, base);
len = 0;
for (HMAP_ITER(&dirmap, iter))
len++;
list = malloc(sizeof(struct asteroid *) * (size_t) len);
assert(list != NULL);
i = 0;
for (HMAP_ITER(&dirmap, iter))
list[i++] = iter.link->value.p;
for (i = 0; i < len; i++) {
for (k = 0; k < len - 1; k++) {
if (angle(list[k], base) > angle(list[k+1], base)) {
tmp = list[k];
list[k] = list[k+1];
list[k+1] = tmp;
}
}
}
prev = angle(list[0], base);
for (k = 0; k < len; k++) {
aoc_debug("%i: %i %i %f\n", k+1, list[k]->x,
list[k]->y, angle(list[k], base));
}
aoc.answer = aprintf("%i", list[199]->x * 100 + list[199]->y);
aoc.solution = "1419";
free(list);
for (HMAP_ITER(&dirmap, iter))
free(iter.link->key._p);
asteroids_deinit();
hmap_deinit(&dirmap);
}
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