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#include <err.h>
#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>
#define ROWCNT 98
#define ROWLEN 98
#ifdef PART2
#define IS_SEAT(a, b) \
if (rows[a][b] == '.') \
continue
#define IS_OCC(a, b) \
if (rows[a][b] == '#') \
adjecent++
#endif
bool changed;
char rows[ROWCNT][ROWLEN + 1];
char temp[ROWCNT][ROWLEN + 1];
/* Check and update a seat at the given index */
static void
check_seat(int const i, int const j)
{
if (rows[i][j] == '.')
return;
int adjecent = 0;
#ifdef PART2
/* Up */
for (int h = i - 1; h >= 0; h--) {
IS_SEAT(h, j);
IS_OCC(h, j);
break;
}
/* Down */
for (int h = i + 1; h < ROWCNT; h++) {
IS_SEAT(h, j);
IS_OCC(h, j);
break;
}
/* Left */
for (int h = j - 1; h >= 0; h--) {
IS_SEAT(i, h);
IS_OCC(i, h);
break;
}
/* Right */
for (int h = j + 1; h < ROWLEN; h++) {
IS_SEAT(i, h);
IS_OCC(i, h);
break;
}
/* Up-Left */
for (int h = i - 1, k = j - 1; h >= 0 && k >= 0; h--, k--) {
IS_SEAT(h, k);
IS_OCC(h, k);
break;
}
/* Up-Right */
for (int h = i - 1, k = j + 1; h >= 0 && k < ROWLEN; h--, k++) {
IS_SEAT(h, k);
IS_OCC(h, k);
break;
}
/* Down-Left */
for (int h = i + 1, k = j - 1; h < ROWCNT && k >= 0; h++, k--) {
IS_SEAT(h, k);
IS_OCC(h, k);
break;
}
/* Down-Right */
for (int h = i + 1, k = j + 1; h < ROWCNT && k < ROWLEN; h++, k++) {
IS_SEAT(h, k);
IS_OCC(h, k);
break;
}
#else
for (int h = i - 1; h <= i + 1; h++) {
if (h < 0 || h > ROWCNT - 1)
continue;
for (int k = j - 1; k <= j + 1; k++) {
if (k < 0 || k > ROWCNT - 1 || (h == i && k == j))
continue;
if (rows[h][k] == '#')
adjecent++;
}
}
#endif
/* Edit seats as needed */
if (rows[i][j] == 'L' && adjecent == 0) {
temp[i][j] = '#';
changed = true;
#ifdef PART2
} else if (rows[i][j] == '#' && adjecent >= 5) {
#else
} else if (rows[i][j] == '#' && adjecent >= 4) {
#endif
temp[i][j] = 'L';
changed = true;
} else
temp[i][j] = rows[i][j];
}
int
main(void)
{
/* Initialize the temp array to be all floor */
int i, j;
for (i = 0; i < ROWCNT; i++) {
for (j = 0; j < ROWLEN; j++)
temp[i][j] = '.';
}
FILE *fp;
if (!(fp = fopen("input", "r")))
err(EXIT_FAILURE, "fopen");
/* Read in seats */
i = j = 0;
char c;
while ((c = fgetc(fp)) != EOF) {
if (c == '\n') {
i = 0;
j++;
} else
rows[j][i++] = c;
}
fclose(fp);
/* Update the seats until they don't change anymore */
do {
changed = false;
for (i = 0; i < ROWCNT; i++) {
for (j = 0; j < ROWLEN; j++)
check_seat(i, j);
}
for (i = 0; i < ROWCNT; i++) {
for (j = 0; j < ROWLEN; j++)
rows[i][j] = temp[i][j];
}
} while (changed);
/* Calculate filled seats */
int count = 0;
for (i = 0; i < ROWCNT; i++) {
for (j = 0; j < ROWLEN; j++) {
if (rows[i][j] == '#')
count++;
}
}
printf("%d\n", count);
return EXIT_SUCCESS;
}
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