2018/day8.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 typedef struct node node;
  18 struct node {
  19   char n_children;
  20   char n_data;
  21   node *children;
  22   char *data;
  23   int value;
  24 };
  25 static node head;
  26 static int count;
  27 static int sum;
  28
  29 void process(FILE *f, node *n) {
  30   int i;
  31   count++;
  32   n->value = 0;
  33   if (fscanf(f, "%hhd %hhd ", &n->n_children, &n->n_data) != 2) {
  34     fprintf(stderr, "unexpected input\n");
  35     exit(1);
  36   }
  37   if (!(n->children = malloc(n->n_children * sizeof(node))) ||
  38       !(n->data = malloc(n->n_data))) {
  39     perror("malloc");
  40     exit(1);
  41   }
  42   for (i = 0; i < n->n_children; i++)
  43     process(f, &n->children[i]);
  44   for (i = 0; i < n->n_data; i++) {
  45     if (fscanf(f, "%hhd ", &n->data[i]) != 1) {
  46       fprintf(stderr, "unexpected input\n");
  47       exit(1);
  48     }
  49     sum += n->data[i];
  50     if (n->n_children) {
  51       if (n->data[i] - 1U < n->n_children)
  52         n->value += n->children[n->data[i] - 1].value;
  53     } else
  54       n->value += n->data[i];
  55   }
  56 }
  57
  58 int main(int argc, char **argv) {
  59   if (argc > 1)
  60     if (!(stdin = freopen(argv[1], "r", stdin))) {
  61       perror("failure");
  62       exit(2);
  63     }
  64
  65   process(stdin, &head);
  66   printf("read %d nodes, metadata sum %d\n", count, sum);
  67   printf("root value %d\n", head.value);
  68   return 0;
  69 }