2 files changed, 115 insertions, 17 deletions

diff --git a/src/2020/day4/aoc.cpp b/src/2020/day4/aoc.cpp
index 171f42e..cd8fb64 100644
--- a/src/2020/day4/aoc.cpp
+++ b/src/2020/day4/aoc.cpp
@@ -2,26 +2,29 @@
 
 namespace aoc2020 {
 
-int day4(line_view file) {
+std::pair<int, int> day4(line_view file) {
   const char* p1 = file.line;
   const char* p2 = file.line + file.length;
   const char* p = p1;
-  int total{0};
+  int t0{0};
+  int t1{0};
+  bool b1{false};
+  bool b2{false};
   while (p < p2) {
     if (*p == '\n' && *(p + 1) == '\n') {
-      passwort pass{p1, p};
+      passport pass{p1, p};
       // std::cout << pass << std::endl;
-      if (pass.is_valid()) {
-        total++;
-      }
+      pass.is_valid(&b1, &b2);
+      t0 += int(b1);
+      t1 += int(b2);
       p1 = p + 2;
     }
     p++;
   }
-  if (passwort{p1, p}.is_valid()) {
-    total++;
-  }
-  return total;
+  passport{p1, p}.is_valid(&b1, &b2);
+  t0 += int(b1);
+  t1 += int(b2);
+  return {t0, t1};
 }
 
 } // namespace aoc2020
diff --git a/src/2020/day4/aoc.h b/src/2020/day4/aoc.h
index a0b42b5..663fa1b 100644
--- a/src/2020/day4/aoc.h
+++ b/src/2020/day4/aoc.h
@@ -4,7 +4,7 @@
 
 namespace aoc2020 {
 
-struct passwort {
+struct passport {
   line_view byr;
   line_view iyr;
   line_view eyr;
@@ -14,19 +14,114 @@ struct passwort {
   line_view pid;
   line_view cid;
 
-  friend std::ostream& operator<<(std::ostream& o, const passwort& p) {
+  friend std::ostream& operator<<(std::ostream& o, const passport& p) {
     o << p.byr << " " << p.iyr << " " << p.eyr << " ";
     o << p.hgt << " " << p.hcl << " " << p.ecl << " ";
     o << p.pid << " " << p.cid << " ";
     return o;
   }
 
-  bool is_valid() const noexcept {
-    return byr.length > 0 && iyr.length > 0 && eyr.length > 0 && hgt.length > 0 && hcl.length > 0 && ecl.length > 0 &&
-           pid.length > 0;
+  void get_number(const char** pp, int* d) {
+    const char* p = *pp;
+    while (*p >= '0' && *p <= '9') {
+      *d = *d * 10 + *p - '0';
+      p++;
+    }
+    *pp = p;
+  }
+
+  typedef bool (passport::*cf)(line_view);
+
+  template <int A, int B, int C>
+  bool chk1(line_view lv) {
+    int y{0};
+    const char* p = lv.line;
+    get_number(&p, &y);
+    return lv.length == A && y >= B && y <= C;
+  }
+
+  bool chk2(line_view lv) {
+    int d{0};
+    const char* p = lv.line;
+    get_number(&p, &d);
+    bool b1 = (*p == 'c' && *(p + 1) == 'm') && d >= 150 && d <= 193;
+    bool b2 = (*p == 'i' && *(p + 1) == 'n') && d >= 59 && d <= 76;
+    return b1 || b2;
+  }
+
+  bool chk3(line_view lv) {
+    static const char* cs[] = {"amb", "blu", "brn", "gry", "grn", "hzl", "oth"};
+    for (auto c : cs) {
+      if (lv == c) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  template <int A, char B, char C>
+  bool chk4(line_view lv) {
+    const char* p = lv.line;
+    for (int i = 0; i < A; i++) {
+      if (*(p + i) < B || *(p + i) > C) {
+        return false;
+      }
+    }
+    return lv.length == A;
+  }
+
+  bool chk5(line_view lv) {
+    const char* p = lv.line + 1;
+    auto is_az = [](char c) { return c >= 'a' && c <= 'z'; };
+    auto is_09 = [](char c) { return c >= '0' && c <= '9'; };
+    while (p < lv.line + lv.length) {
+      if (!is_az(*p) && !is_09(*p)) {
+        return false;
+      }
+      p++;
+    }
+    return *lv.line == '#' && lv.length == 7;
+  }
+
+  // byr (Birth Year) - four digits; at least 1920 and at most 2002.
+  // iyr (Issue Year) - four digits; at least 2010 and at most 2020.
+  // eyr (Expiration Year) - four digits; at least 2020 and at most 2030.
+  // hgt (Height) - a number followed by either cm or in:
+  // If cm, the number must be at least 150 and at most 193.
+  // If in, the number must be at least 59 and at most 76.
+  // hcl (Hair Color) - a # followed by exactly six characters 0-9 or a-f.
+  // ecl (Eye Color) - exactly one of: amb blu brn gry grn hzl oth.
+  // pid (Passport ID) - a nine-digit number, including leading zeroes.
+  // cid (Country ID) - ignored, missing or not.
+
+  void is_valid(bool* b1, bool* b2) {
+    *b1 = byr.length > 0 && iyr.length > 0 && eyr.length > 0 && hgt.length > 0 && hcl.length > 0 && ecl.length > 0 &&
+          pid.length > 0;
+
+    *b2 = false;
+    if (*b1) {
+      struct {
+        cf f;
+        line_view* field;
+      } checkers[] = {
+          {&passport::chk1<4, 1920, 2002>, &byr},
+          {&passport::chk1<4, 2010, 2020>, &iyr},
+          {&passport::chk1<4, 2020, 2030>, &eyr},
+          {&passport::chk2, &hgt},
+          {&passport::chk5, &hcl},
+          {&passport::chk3, &ecl},
+          {&passport::chk4<9, '0', '9'>, &pid},
+      };
+      for (auto c : checkers) {
+        if (!((this->*(c.f))(*c.field))) {
+          return;
+        }
+      }
+      *b2 = true;
+    }
   }
 
-  passwort(const char* p1, const char* p2) {
+  passport(const char* p1, const char* p2) {
     struct {
       line_view* field;
       const char* label;
@@ -64,5 +159,5 @@ struct passwort {
   }
 };
 
-int day4(line_view);
+std::pair<int, int> day4(line_view);
 } // namespace aoc2020