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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
int
main(int argc, char ** argv)
{
int part = 1, cyclelimit = 220;
int cycle;
char buf[BUFSIZ];
char * op, * arg;
int opcycles = 0;
int rx = 1, nextread = 20, interval = 40, total = 0;
while ((cycle = getopt(argc, argv, "p:")) != -1) {
switch (cycle) {
case 'p':
part = atoi(optarg);
switch (part) {
case 1: cyclelimit = 220; break;
case 2: cyclelimit = 1000; break;
default:
fprintf(stderr, "Unexpected part: %d\n", part);
return -1;
}
break;
default:
return -1;
}
}
for (cycle = 1; cycle <= cyclelimit; ++cycle) {
// Start of cycle. Do we need to read a new instruction?
if (opcycles == 0) {
char * toksave = NULL;
if (!fgets(buf, sizeof(buf), stdin))
break;
op = strtok_r(buf, " \n", &toksave);
arg = strtok_r(NULL, "\n", &toksave);
// Just read instruction. Set op cycle count, and
// perform any immediate actions
if (strcmp(op, "noop") == 0 && !arg) {
opcycles = 1;
}
else if (strcmp(op, "addx") == 0 && arg) {
opcycles = 2;
}
else {
fprintf(stderr, "Unexpected op/arg: %s/%s\n", op, arg ? arg : "(null)");
return -1;
}
}
// Mid-cycle debugger attachment.
if (part == 1 && cycle >= nextread) {
total += rx * cycle;
nextread += interval;
}
// Mid-cycle CRT output.
if (part == 2) {
int pixel = (cycle - 1) % interval;
int insprite = pixel >= rx - 1 && pixel <= rx + 1;
fputc(insprite ? '#' : '.', stdout);
if (pixel == interval - 1)
fputc('\n', stdout);
}
// Perform cycle. Reduce opcycle count, do actions that occur on
// op completion and increment cycle counter.
--opcycles;
if (opcycles == 0) {
if (strcmp(op, "addx") == 0) {
rx += atoi(arg);
}
}
}
if (part == 1)
printf("Sum of interesting signal strengths: %d\n", total);
return 0;
}
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