aoc day 4

part2.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void)
{     FILE *f = fopen("input.txt", "r");
      char line[BUFSIZ], key[3], val[BUFSIZ], *p;
      char *eyes[] = {"amb", "blu", "brn", "gry", "grn", "hzl", "oth", 0};
      int docok = 0, subok, loffs, n, r, d;
 doc: if (feof(f) || ferror(f)) goto quit;
      subok = 0;
line: if (!fgets(line, BUFSIZ, f) || strlen(line) == 1) goto stamp;
      loffs = 0;
      while (sscanf(line + loffs, "%3c:%s%n", key, val, &n) == 2)
    { loffs += n + 1; p = val; if (0) {
#define WHEN(_a) } else if (memcmp(#_a, key, 3) == 0) {
#define BETWEEN(_lo, _hi) { r = d >= _lo && d <= _hi; }
#define MAXDIGITS(_digits) { if (sscanf(p, "%d%n", &d, &n) == 1 && n <= _digits) { p += n; r = 1; } else r = 0; }
#define PRED(_n, _q) { for (n = 0;; n++) { char c = *p; if (c && (_q)) p++; else break; } r = n == _n; }
#define NEXT(_str) (strcmp(#_str, p) == 0)
#define AND { if (!r) continue; }
#define DONE { if (r) goto ok; }

  WHEN(byr)  MAXDIGITS(4) AND BETWEEN(1920, 2022) DONE
  WHEN(iyr)  MAXDIGITS(4) AND BETWEEN(2010, 2020) DONE
  WHEN(eyr)  MAXDIGITS(4) AND BETWEEN(2020, 2030) DONE
  WHEN(hgt)  MAXDIGITS(3) AND if NEXT(cm) { BETWEEN(150, 193) DONE }
                              if NEXT(in) { BETWEEN( 59,  76) DONE }
  WHEN(hcl)  PRED(1, c == '#') AND
             PRED(6, (c >= 'a' && c <= 'f') || (c >= '0' && c <= '9')) DONE
  WHEN(ecl)  for (char **e = eyes; *e; e++) if (strcmp(p, *e) == 0) goto ok;
  WHEN(pid)  PRED(9, c >= '0' && c <= '9') DONE

        } continue; ok: subok++; } goto line;
stamp: if (subok == 7) docok++;
       goto doc;
 quit: printf("%d\n", docok); }