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#include "aoc.h"
#include "util.h"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#define MAXA(a, b) (ABS(a) > ABS(b) ? (a) : (b))
#define MINA(a, b) (ABS(a) > ABS(b) ? (b) : (a))
struct line {
int sx, sy;
int ex, ey;
struct line *next;
};
struct line *
parse_lines(const char **pos, const char *end)
{
char buf[2048], part[64];
const char *lpos, *lend;
struct line *line, *start, **iter;
int x, y, val;
aoc_debug("START\n");
if (!readtok(buf, sizeof(buf), '\n', pos, end))
die("parse_lines: end of file");
start = line = NULL;
iter = &line;
x = y = 0;
lpos = buf;
lend = buf + strlen(buf);
while (readtok(part, sizeof(part), ',', &lpos, lend)) {
*iter = line = malloc(sizeof(struct line));
if (!line) die("parse_lines: oom");
if (!start) start = line;
line->next = NULL;
line->sx = x;
line->sy = y;
val = (int) parsei64(part+1);
switch (part[0]) {
case 'L':
x -= val;
break;
case 'R':
x += val;
break;
case 'D':
y -= val;
break;
case 'U':
y += val;
break;
default:
die("parse_lines: invalid move: %s", part);
}
aoc_debug("%i %i\n", x, y);
line->ex = x;
line->ey = y;
iter = &(*iter)->next;
}
aoc_debug("END\n");
return start;
}
void
free_lines(struct line *line)
{
struct line *next;
while (line) {
next = line->next;
free(line);
line = next;
}
}
int
do_intersect(struct line *l1, struct line *l2)
{
int inx, iny;
inx = MAX(l1->sx, l1->ex) >= MIN(l2->sx, l2->ex)
&& MAX(l2->sx, l2->ex) >= MIN(l1->sx, l1->ex);
iny = MAX(l1->sy, l1->ey) >= MIN(l2->sy, l2->ey)
&& MAX(l2->sy, l2->ey) >= MIN(l1->sy, l1->ey);
return inx && iny;
}
void
intersection_near_origin(struct line *l1, struct line *l2, int *x, int *y)
{
if (l1->sx == l1->ex && l2->sx == l2->ex) {
*x = l1->sx;
*y = MAXA(
MINA(l1->sy, l1->ey),
MINA(l2->sy, l2->ey)
);
} else if (l1->sy == l1->ey && l2->sy == l2->ey) {
*y = l1->sy;
*x = MAXA(
MINA(l1->sx, l1->ex),
MINA(l2->sy, l2->ey)
);
} else {
*x = (l1->sx == l1->ex) ? l1->sx : l2->sx;
*y = (l1->sy == l1->ey) ? l1->sy : l2->sy;
}
}
void
intersection_least_steps(struct line *l1, struct line *l2, int *x, int *y)
{
int in1, in2;
if (l1->sx == l1->ex && l2->sx == l2->ex) {
/* if both ends or both starts of lines are part of the intersection,
* any one of them will give the same best dist,
* otherwise the start that intersects is the best fit */
*x = l1->sx;
in1 = l1->sy <= MAX(l2->sy, l2->ey) && l1->sy >= MIN(l2->sy, l2->ey);
in2 = l2->sy <= MAX(l1->sy, l1->ey) && l2->sy >= MIN(l1->sy, l1->ey);
*y = in1 ? l1->sy : (in2 ? l2->sy : l2->ey);
} else if (l1->sy == l1->ey && l2->sy == l2->ey) {
/* same for x-axis */
*y = l1->sy;
in1 = l1->sx <= MAX(l2->sx, l2->ex) && l1->sx >= MIN(l2->sx, l2->ex);
in2 = l2->sx <= MAX(l1->sx, l1->ex) && l2->sx >= MIN(l1->sx, l1->ex);
*x = in1 ? l1->sx : (in2 ? l2->sx : l2->ex);
} else {
*x = (l1->sx == l1->ex) ? l1->sx : l2->sx;
*y = (l1->sy == l1->ey) ? l1->sy : l2->sy;
}
}
int
calc_dist(struct line *lines, struct line *end, int x, int y)
{
struct line *iter;
int dist;
dist = 0;
for (iter = lines; iter != end; iter = iter->next) {
dist += ABS(iter->ex - iter->sx);
dist += ABS(iter->ey - iter->sy);
aoc_debug("D: %i\n", dist);
}
dist += ABS(x - iter->sx);
dist += ABS(y - iter->sy);
aoc_debug("D: %i\n", dist);
return dist;
}
void
part1(void)
{
struct line *lines1, *lines2;
struct line *iter1, *iter2;
const char *pos, *end;
int nx, ny, hit;
int x, y;
pos = aoc.input;
end = aoc.input + aoc.input_size;
lines1 = parse_lines(&pos, end);
lines2 = parse_lines(&pos, end);
x = y = 0;
for (iter1 = lines1; iter1; iter1 = iter1->next) {
for (iter2 = lines2; iter2; iter2 = iter2->next) {
hit = do_intersect(iter1, iter2);
if (!hit) continue;
intersection_near_origin(iter1, iter2, &nx, &ny);
if (!x && !y || ABS(nx) + ABS(ny) < ABS(x) + ABS(y)) {
x = nx;
y = ny;
}
}
}
aoc_debug("dist(%i, %i) = %i\n", x, y, ABS(x) + ABS(y));
aoc.answer = aprintf("%i", ABS(x) + ABS(y));
aoc.solution = "209";
free_lines(lines1);
free_lines(lines2);
}
void
part2(void)
{
struct line *lines1, *lines2;
struct line *iter1, *iter2;
const char *pos, *end;
int nx, ny, nd, hit;
int x, y, d;
pos = aoc.input;
end = aoc.input + aoc.input_size;
lines1 = parse_lines(&pos, end);
lines2 = parse_lines(&pos, end);
x = y = 0;
for (iter1 = lines1; iter1; iter1 = iter1->next) {
for (iter2 = lines2; iter2; iter2 = iter2->next) {
hit = do_intersect(iter1, iter2);
if (!hit) continue;
intersection_least_steps(iter1, iter2, &nx, &ny);
nd = calc_dist(lines1, iter1, nx, ny);
nd += calc_dist(lines2, iter2, nx, ny);
if (!x && !y || nd < d) {
d = nd;
x = nx;
y = ny;
}
}
}
aoc_debug("steps(%i, %i) = %i\n", x, y, d);
aoc.answer = aprintf("%i", d);
aoc.solution = "43258";
free_lines(lines1);
free_lines(lines2);
}
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