2016/advent20.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 #define MAX 1200 // cheat, by using wc on input file
  10 typedef struct entry entry;
  11 struct entry {
  12   unsigned int lo;
  13   unsigned int hi;
  14 };
  15 entry list[MAX];
  16
  17 int
  18 compare (const void *a, const void *b)
  19 {
  20   const entry *e1 = a, *e2 = b;
  21   return e1->lo < e2->lo ? -1 : e1->lo > e2->lo;
  22 }
  23
  24 int
  25 main (int argc, char **argv)
  26 {
  27   int count = 0;
  28   unsigned int lo, hi;
  29   while (scanf ("%d-%d\n", &lo, &hi) == 2) {
  30     list[count].lo = lo;
  31     list[count].hi = hi;
  32     count++;
  33   }
  34   qsort (list, count, sizeof *list, compare);
  35   printf ("read and sorted %d entries\n", count);
  36   unsigned int min = 0;
  37   unsigned int total = 0;
  38   for (int i = 0; i < count; i++) {
  39     if (min < list[i].lo) {
  40       total += list[i].lo - min;
  41       min = list[i].lo;
  42     }
  43     if (list[i].lo <= min && list[i].hi >= min) {
  44       min = list[i].hi + 1;
  45       if (!min)
  46         break;
  47     }
  48   }
  49   if (list[count - 1].hi < -1U)
  50     total -= min;
  51   printf ("total %u\n", total);
  52   return 0;
  53 }