2018/day7b.c

   1 #define _GNU_SOURCE 1
   2 #include <stdio.h>
   3 #include <string.h>
   4 #include <stdlib.h>
   5 #include <stdarg.h>
   6 #include <stdbool.h>
   7
   8 void debug(const char *fmt, ...) {
   9   va_list ap;
  10   if (getenv("DEBUG")) {
  11     va_start(ap, fmt);
  12     vfprintf(stderr, fmt, ap);
  13     va_end(ap);
  14   }
  15 }
  16
  17 static struct data {
  18   char state;
  19   char wait[26];
  20 } list[26];
  21
  22 int main(int argc, char **argv) {
  23   size_t len = 0, count = 0;
  24   char *line;
  25   int i, j;
  26   char a, b;
  27   char *p;
  28   int offset = 60;
  29   int workers = 5;
  30   char work[5] = "";
  31
  32   /* Part 1 - read in lines */
  33   if (argc > 2)
  34     offset = atoi(argv[2]);
  35   if (argc > 3)
  36     workers = atoi(argv[3]);
  37   if (argc > 1)
  38     if (!(stdin = freopen(argv[1], "r", stdin))) {
  39       perror("failure");
  40       exit(2);
  41     }
  42
  43   while (getline(&line, &len, stdin) >= 0) {
  44     ++count;
  45     if (sscanf(line, "Step %c must be finished before step %c can begin. ", &a,
  46                &b) != 2 || (unsigned)(a-'A') > 25 || (unsigned)(b-'A') > 25) {
  47       fprintf(stderr, "bad input\n");
  48       exit(1);
  49     }
  50     list[a - 'A'].state = a - 'A' + 1 + offset;
  51     list[b - 'A'].state = b - 'A' + 1 + offset;
  52     strchrnul(list[b - 'A'].wait, '\0')[0] = a;
  53   }
  54   printf("Read %zu lines\n", count);
  55
  56   /* Part 2 - determine output */
  57   count = 0;
  58   do {
  59     count++;
  60     for (j = 0; j < workers; j++)
  61       if (work[j])
  62         if (!++list[work[j] - 'A'].state)
  63           work[j] = 0;
  64     for (j = 0; j < workers; j++) {
  65       if (work[j])
  66         continue;
  67       for (i = 0; i < 26; i++) {
  68         if (list[i].state <= 0)
  69           continue;
  70         p = list[i].wait;
  71         while (*p) {
  72           if (list[*p - 'A'].state)
  73             break;
  74           p++;
  75         }
  76         if (*p)
  77           continue;
  78         list[i].state = -list[i].state;
  79         work[j] = i + 'A';
  80         debug("time %zu worker %d starting job %c\n", count - 1, j, i + 'A');
  81         break;
  82       }
  83     }
  84   } while (work[0] || work[1] || work[2] || work[3] || work[4]);
  85   printf("took %zu seconds\n", count - 1);
  86   return 0;
  87 }