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#include <assert.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
enum {
WIDTH = 1000,
HEIGHT = 1000,
};
struct instr {
signed char db;
struct pos {
unsigned short x, y;
} start, end;
};
unsigned short read_be16(void *_buf)
{
unsigned char *buf = _buf;
return (buf[0] << 8) | buf[1];
}
bool read_instr(struct instr *i, FILE *f)
{
unsigned char buf[9];
signed char db;
unsigned short v;
assert(i != NULL);
assert(f != NULL);
if (fread(buf, sizeof buf, 1, f) != 1)
return false;
if (buf[0] <= 127)
db = buf[0];
else {
db = -0x80;
db += buf[0] - 0x80;
}
if (db < -1 || db > 2) {
fprintf(stderr, "this db is crazy: %d -> %d\n", buf[0], db);
return false;
}
i->db = db;
#define SET(f, p) { \
v = read_be16(&buf[p]); \
if (v > 999) \
return false; \
i->f = v; \
}
SET(start.x, 1);
SET(start.y, 3);
SET(end.x, 5);
SET(end.y, 7);
return true;
}
int main(void)
{
int screen[WIDTH][HEIGHT] = { 0 };
unsigned long long total;
struct instr i;
FILE *f;
f = fopen("inputbin", "rb");
if (f == NULL)
exit(EXIT_FAILURE);
while (read_instr(&i, f)) {
for (int y = i.start.y; y <= i.end.y; y++) {
for (int x = i.start.x; x <= i.end.x; x++) {
screen[x][y] += i.db;
if (screen[x][y] < 0)
screen[x][y] = 0;
}
}
}
fclose(f);
total = 0;
for (int y = 0; y < HEIGHT; y++)
for (int x = 0; x < WIDTH; x++)
total += screen[x][y];
printf("%llu\n", total);
}
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