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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#if 0
#define PART part1
#else
#define PART part2
#endif
#if 0
#define FILENAME "sample.txt"
#define WIDTH 600
#define HEIGHT 20
#else
#define FILENAME "input.txt"
#define WIDTH 2000
#define HEIGHT 500
#endif
#define MAX(x, y) (((x) > (y)) ? (x) : (y))
#define MIN(x, y) (((x) < (y)) ? (x) : (y))
int map[WIDTH][HEIGHT] = {0};
int max_y = INT_MIN;
int sands = 0;
int sim_sand()
{
int sand_x = 500;
int sand_y = 0;
while(1) {
if(sand_y >= max_y)
return -1;
if(map[sand_x][sand_y + 1] != 1) {
sand_y++;
} else if(map[sand_x - 1][sand_y + 1] != 1) {
sand_x--; sand_y++;
} else if(map[sand_x + 1][sand_y + 1] != 1) {
sand_x++; sand_y++;
} else break;
continue;
}
map[sand_x][sand_y] = 1;
return 0;
}
void part1()
{
while(sim_sand() == 0)
sands++;
}
void draw_line(int x1, int y1, int x2, int y2);
void part2()
{
draw_line(0, max_y + 2, WIDTH-1, max_y + 2);
max_y = INT_MAX;
while(map[500][0] != 1) {
sim_sand();
sands++;
}
}
void draw_line(int x1, int y1, int x2, int y2)
{
if(x1 != x2 && y1 == y2)
for(int x = MIN(x1, x2); x <= MAX(x1, x2); x++)
map[x][y1] = 1;
else if(y1 != y2 && x1 == x2)
for(int y = MIN(y1, y2); y <= MAX(y1, y2); y++)
map[x1][y] = 1;
}
void parse()
{
FILE *fp = fopen(FILENAME, "r");
if(!fp) {
fprintf(stderr, "ERROR: Could not open file %s\n", FILENAME);
exit(1);
}
char line[5000];
while(fgets(line, sizeof(line), fp))
{
int x1 = -1; int y1 = -1;
int x2 = -1; int y2 = -1;
char *sprt1;
char *tok = strtok_r(line, " -> ", &sprt1);
while(tok != NULL) {
char *sprt2;
x2 = atoi(strtok_r(tok, ",", &sprt2));
y2 = atoi(strtok_r(NULL, ",", &sprt2));
max_y = MAX(max_y, y2);
if(x1 != -1 && y1 != -1)
draw_line(x1, y1, x2, y2);
x1 = x2; y1 = y2;
tok = strtok_r(NULL, " -> ", &sprt1);
}
}
fclose(fp);
}
int main(void)
{
parse();
PART();
printf("%d\n", sands);
return 0;
}
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