2019/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 static int debug_level = -1;
   9 static void
  10 debug_raw(int level, const char *fmt, ...) {
  11   va_list ap;
  12   if (debug_level < 0)
  13     debug_level = atoi(getenv("DEBUG") ?: "0");
  14   if (debug_level >= level) {
  15     va_start(ap, fmt);
  16     vfprintf(stderr, fmt, ap);
  17     va_end(ap);
  18   }
  19 }
  20 #define debug(...) debug_raw(1, __VA_ARGS__)
  21
  22 #define MAXX 25
  23 #define MAXY 6
  24 static char grid[MAXY][MAXX];
  25 static int x = MAXX;
  26 static int y = MAXY;
  27
  28 static void
  29 dump(int level) {
  30   int i, j;
  31   if (debug_level < level)
  32     return;
  33   putchar('\n');
  34   for (j = 0; j < y; j++) {
  35     for (i = 0; i < x; i++)
  36       putchar(" X-"[grid[j][i] - '0']);
  37     putchar('\n');
  38   }
  39 }
  40
  41 int
  42 main(int argc, char **argv) {
  43   int zero = 0, one = 0, two = 0, min, best, count = 0, page, ch;
  44   bool done = false;
  45
  46   debug("");
  47   memset(grid, '2', sizeof grid);
  48   if (argc > 2) {
  49     x = atoi(argv[1]);
  50     y = atoi(argv[2]);
  51   }
  52   else if (argc > 1)
  53     if (!(stdin = freopen(argv[1], "r", stdin))) {
  54       perror("failure");
  55       exit(2);
  56     }
  57
  58   min = page = x * y;
  59
  60   while (!done) {
  61     ch = getchar();
  62     switch (ch) {
  63     case '0':
  64       zero++;
  65       break;
  66     case '1':
  67       one++;
  68       break;
  69     case '2':
  70       two++;
  71       break;
  72     default:
  73       done = true;
  74       break;
  75     }
  76     if (grid[(count/x)%y][count%x] == '2')
  77       grid[(count/x)%y][count%x] = ch;
  78     if (!(count++ % page)) {
  79       if (zero < min) {
  80         min = zero;
  81         best = one * two;
  82       }
  83       zero = one = two = 0;
  84       dump(1);
  85     }
  86   }
  87   printf("read %d bytes, best page value %d\n", count, best);
  88   dump(0);
  89
  90   return 0;
  91 }