2017/advent15.c

   1 #define _GNU_SOURCE 1
   2 #include <stdio.h>
   3 #include <string.h>
   4 #include <stdlib.h>
   5 #include <unistd.h>
   6
   7 int main(int argc, char **argv)
   8 {
   9   if (argc != 3)
  10     return 1;
  11   unsigned int a = atoi (argv[1]);
  12   unsigned int b = atoi (argv[2]);
  13   int match = 0;
  14   for (int i = 0; i < 5000000; i++) {
  15     do {
  16       a = a * 16807ULL % 2147483647;
  17     } while (a % 4);
  18     do {
  19       b = b * 48271ULL % 2147483647;
  20     } while (b % 8);
  21     if ((a & 0xffff) == (b & 0xffff))
  22       match++;
  23   }
  24   printf ("total matches: %d\n", match);
  25   return 0;
  26 }