2016/advent7.c

   1 #define _GNU_SOURCE 1
   2 #include <stdio.h>
   3 #include <string.h>
   4 #include <stdlib.h>
   5 #include <unistd.h>
   6 #include <stdbool.h>
   7 #include <ctype.h>
   8
   9 bool
  10 check (const char *s)
  11 {
  12   int len = strlen (s);
  13   printf ("checking %s\n", s);
  14   for (int i = 0; i < len - 3; i++)
  15     if (s[i] != s[i + 1] && s[i + 1] == s[i + 2] && s[i] == s[i + 3])
  16       return true;
  17   printf ("no abba\n");
  18   return false;
  19 }
  20
  21 char *
  22 find (char *s)
  23 {
  24   while (*s && s[1] && s[2]) {
  25     if (s[0] != s[1] && s[0] == s[2])
  26       return s;
  27     s++;
  28   }
  29   return NULL;
  30 }
  31
  32 bool
  33 match (const char *h, const char *patt)
  34 {
  35   char n[4] = { patt[1], patt[0], patt[1] };
  36   printf ("looking for %s in %s\n", n, h);
  37   return strstr (h, n);
  38 }
  39
  40 int main(int argc, char **argv)
  41 {
  42   ssize_t nread;
  43   size_t len = 0;
  44   char *line = NULL;
  45   int count1 = 0, count2 = 0;
  46   char super[80], hyper[80];
  47   while ((nread = getline(&line, &len, stdin)) >= 0) {
  48     line[nread - 1] = '\0';
  49     char *p = line;
  50     printf ("parsing %s\n", line);
  51     super[0] = hyper[0] = '\0';
  52     char *s = super, *h = hyper;
  53     char goal = '[';
  54     while (*p) {
  55       char *q = strchrnul (p, goal);
  56       if (goal == '[')
  57         s += sprintf (s, "%.*s[]", (int) (q - p), p);
  58       else
  59         h += sprintf (h, "%.*s ", (int) (q - p), p);
  60       p = q + !!*q;
  61       goal ^= 6; // cute ascii toggle between [ and ]
  62     }
  63     if (check (s = super) && ! check (hyper))
  64       count1++;
  65     while ((s = find (s)))
  66       if (match (hyper, s++)) {
  67         count2++;
  68         break;
  69       }
  70   }
  71   printf ("final count: TLS %d, SSL %d\n", count1, count2);
  72   return 0;
  73 }