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#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#define SIZE 10000
#define X_MAX 99
#define Y_MAX 97
// Quite magical, isn't it?
#define TOP_LEFT(x, y, p) (x != 0 && y != 0 ? *(p - X_MAX - 1) : 0)
#define TOP_CENTER(x, y, p) (y != 0 ? *(p - X_MAX) : 0)
#define TOP_RIGHT(x, y, p) (x != X_MAX && y != 0 ? *(p - X_MAX + 1) : 0)
#define LEFT(x, y, p) (x != 0 ? *(p - 1) : 0)
#define RIGHT(x, y, p) (x != X_MAX ? *(p + 1) : 0)
#define BOTTOM_LEFT(x, y, p) (x != 0 && y != Y_MAX ? *(p + X_MAX - 1) : 0)
#define BOTTOM_CENTER(x, y, p) (y != Y_MAX ? *(p + X_MAX) : 0)
#define BOTTOM_RIGHT(x, y, p) (x != X_MAX && y != Y_MAX ? *(p + X_MAX + 1) : 0)
#define ADJACENT(x, y, p) \
((TOP_LEFT(x, y, p) == '#') + (TOP_CENTER(x, y, p) == '#') + (TOP_RIGHT(x, y, p) == '#') + \
(LEFT(x, y, p) == '#') + (RIGHT(x, y, p) == '#') + (BOTTOM_LEFT(x, y, p) == '#') + \
(BOTTOM_CENTER(x, y, p) == '#') + (BOTTOM_RIGHT(x, y, p) == '#'))
int count_one(char *buf1, char *buf2)
{
int x = 0, y = 0;
for (char *p = buf1; *p; p++) {
if (*p == '.') {
x++;
buf2[p - buf1] = '.';
continue;
}
if (*p == '\n') {
x = 0;
y++;
buf2[p - buf1] = '\n';
continue;
}
int cnt = ADJACENT(x, y, p);
if (*p == 'L' && !cnt) {
buf2[p - buf1] = '#';
} else if (*p == '#' && cnt >= 4) {
buf2[p - buf1] = 'L';
} else {
buf2[p - buf1] = *p;
}
x++;
}
if (memcmp(buf1, buf2, SIZE)) {
return count_one(buf2, buf1); // Swap buffers
} else {
int cnt = 0;
for (char *p = buf1; *p; p++) {
if (*p == '#')
cnt++;
}
return cnt;
}
}
#define TL (1 << 0)
#define TC (1 << 1)
#define TR (1 << 2)
#define R (1 << 3)
#define BR (1 << 4)
#define BC (1 << 5)
#define BL (1 << 6)
#define L (1 << 7)
#define SET(d) \
{ \
if (type == '#' || type == 'L') \
found |= d; \
if (type == '#') \
cnt++; \
}
int count_two(char *buf1, char *buf2)
{
int x = 0, y = 0;
for (char *p = buf1; *p; p++) {
if (*p == '.') {
x++;
buf2[p - buf1] = '.';
continue;
}
if (*p == '\n') {
x = 0;
y++;
buf2[p - buf1] = '\n';
continue;
}
int i = 0, found = 0, cnt = 0;
char type;
while (found != 0xff) {
// Handle overflows (could be combined with the checks below)
if (x - i <= 0 || y - i <= 0)
found |= TL;
if (y - i <= 0)
found |= TC;
if (x + i >= X_MAX - 2 || y - i <= 0)
found |= TR;
if (x + i >= X_MAX - 2)
found |= R;
if (x + i >= X_MAX - 2 || y + i >= Y_MAX)
found |= BR;
if (y + i >= Y_MAX)
found |= BC;
if (x - i <= 0 || y + i >= Y_MAX)
found |= BL;
if (x - i <= 0)
found |= L;
// Find next seat
if ((found & TL) == 0 &&
(type = TOP_LEFT(x - i, y - i, &buf1[(y - i) * X_MAX + (x - i)])))
SET(TL);
if ((found & TC) == 0 &&
(type = TOP_CENTER(x, y - i, &buf1[(y - i) * X_MAX + x])))
SET(TC);
if ((found & TR) == 0 &&
(type = TOP_RIGHT(x + i, y - i, &buf1[(y - i) * X_MAX + (x + i)])))
SET(TR);
if ((found & R) == 0 &&
(type = RIGHT(x + i, y, &buf1[y * X_MAX + (x + i)])))
SET(R);
if ((found & BR) == 0 &&
(type = BOTTOM_RIGHT(x + i, y + i, &buf1[(y + i) * X_MAX + (x + i)])))
SET(BR);
if ((found & BC) == 0 &&
(type = BOTTOM_CENTER(x, y + i, &buf1[(y + i) * X_MAX + x])))
SET(BC);
if ((found & BL) == 0 &&
(type = BOTTOM_LEFT(x - i, y + i, &buf1[(y + i) * X_MAX + (x - i)])))
SET(BL);
if ((found & L) == 0 && (type = LEFT(x - i, y, &buf1[y * X_MAX + (x - i)])))
SET(L);
i++;
}
if (*p == 'L' && !cnt) {
buf2[p - buf1] = '#';
} else if (*p == '#' && cnt >= 5) {
buf2[p - buf1] = 'L';
} else {
buf2[p - buf1] = *p;
}
x++;
}
if (memcmp(buf1, buf2, SIZE)) {
return count_two(buf2, buf1); // Swap buffers
} else {
int cnt = 0;
for (char *p = buf1; *p; p++) {
if (*p == '#')
cnt++;
}
return cnt;
}
}
int part_one(char *data)
{
int res = 0;
char buf1[SIZE] = { 0 };
memcpy(buf1, data, SIZE);
char buf2[SIZE] = { 0 };
memcpy(buf2, data, SIZE);
return count_one(buf1, buf2);
}
int part_two(char *data)
{
int res = 0;
char buf1[SIZE] = { 0 };
memcpy(buf1, data, SIZE);
char buf2[SIZE] = { 0 };
memcpy(buf2, data, SIZE);
return count_two(buf1, buf2);
}
int main(int argc, char *argv[])
{
FILE *fp = fopen("input", "r");
if (!fp)
exit(EXIT_FAILURE);
char buf[SIZE] = { 0 };
fread(buf, SIZE, 1, fp);
clock_t tic = clock();
printf("%d\n", part_one(buf));
printf("%d\n", part_two(buf));
clock_t toc = clock();
printf("TIME: %f seconds\n", (double)(toc - tic) / CLOCKS_PER_SEC);
fclose(fp);
return 0;
}
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