Day 15: Warehouse Woes
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C
3h+ train ride back home from weekend trip but a little tired and not feeling it much. Finished part 1, saw that part 2 was fiddly programming, left it there.
Finally hacked together something before bed. The part 2 twist required rewriting the push function to be recursive but also a little care and debugging to get that right. Cleaned it up over lunch, happy enough with the solution now!
Code
#include "common.h"
#define GW 104
#define GH 52
struct world { char g[GH][GW]; int px,py; };
static int
can_clear(struct world *w, int x, int y, int dx, int dy)
{
assert(x>=0); assert(x<GW);
assert(y>=0); assert(y<GH);
assert((dx && !dy) || (dy && !dx));
return
(x+dx >= 0 || x+dx < GW) &&
(y+dy >= 0 || y+dy < GW) &&
(w->g[y][x] == '.' || (
w->g[y][x] != '#' && can_clear(w, x+dx,y+dy, dx,dy) &&
(!dy || w->g[y][x]!='[' || can_clear(w, x+1,y+dy, 0,dy)) &&
(!dy || w->g[y][x]!=']' || can_clear(w, x-1,y, 0,dy)) &&
(!dy || w->g[y][x]!=']' || can_clear(w, x-1,y+dy, 0,dy))));
}
/* check can_clear() first! */
static void
clear(struct world *w, int x, int y, int dx, int dy)
{
assert(x>=0); assert(x<GW); assert(x+dx>=0); assert(x+dx<GW);
assert(y>=0); assert(y<GH); assert(y+dy>=0); assert(y+dy<GH);
if (w->g[y][x] == '.')
return;
if (dy && w->g[y][x] == ']')
{ clear(w, x-1,y, dx,dy); return; }
if (dy && w->g[y][x] == '[') {
clear(w, x+1,y+dy, dx,dy);
w->g[y+dy][x+dx+1] = ']';
w->g[y][x+1] = '.';
}
clear(w, x+dx,y+dy, dx,dy);
w->g[y+dy][x+dx] = w->g[y][x];
w->g[y][x] = '.';
}
static void
move(struct world *w, int dx, int dy)
{
if (can_clear(w, w->px+dx, w->py+dy, dx,dy)) {
clear(w, w->px+dx, w->py+dy, dx,dy);
w->px += dx;
w->py += dy;
}
}
static int
score(struct world *w)
{
int acc=0, x,y;
for (y=0; y<GH && w->g[y][0]; y++)
for (x=0; x<GW && w->g[y][x]; x++)
if (w->g[y][x] == 'O' || w->g[y][x] == '[')
acc += 100*y + x;
return acc;
}
int
main(int argc, char **argv)
{
static struct world w1,w2;
int x,y, c;
char *p;
if (argc > 1)
DISCARD(freopen(argv[1], "r", stdin));
for (y=0; fgets(w1.g[y], GW, stdin); y++) {
if (!w1.g[y][0] || w1.g[y][0]=='\n')
break;
assert(y+1 < GH);
assert(strlen(w1.g[y])*2+1 < GW);
for (x=0; w1.g[y][x]; x++)
if (w1.g[y][x] == 'O') {
w2.g[y][x*2] = '[';
w2.g[y][x*2+1] = ']';
} else {
w2.g[y][x*2] = w1.g[y][x];
w2.g[y][x*2+1] = w1.g[y][x];
}
if ((p = strchr(w1.g[y], '@'))) {
w1.py = y; w1.px = p-w1.g[y];
w2.py = y; w2.px = w1.px*2;
w1.g[w1.py][w1.px] = '.';
w2.g[w2.py][w2.px] = '.';
w2.g[w2.py][w2.px+1] = '.';
}
}
while ((c = getchar()) != EOF)
switch (c) {
case '^': move(&w1, 0,-1); move(&w2, 0,-1); break;
case 'v': move(&w1, 0, 1); move(&w2, 0, 1); break;
case '<': move(&w1,-1, 0); move(&w2,-1, 0); break;
case '>': move(&w1, 1, 0); move(&w2, 1, 0); break;
}
printf("15: %d %d\n", score(&w1), score(&w2));
return 0;
}
