4

Author: gogsbread

cpp/4.cpp

@@ -0,0 +1,47 @@
+#include "common.h"
+
+namespace {
+auto parse(const std::string &s) {
+  auto it = std::find(s.begin(), s.end(), ',');
+  std::string_view sec1{s.begin(), it};
+  std::string_view sec2{std::next(it, 1), s.end()};
+  std::tuple<long, long, long, long> out{};
+  {
+    size_t hy = sec1.find('-');
+    std::from_chars(sec1.data(), sec1.data() + hy, std::get<0>(out));
+    std::from_chars(sec1.data() + hy + 1, sec1.data() + sec1.size(),
+                    std::get<1>(out));
+  }
+  {
+    size_t hy = sec2.find('-');
+    std::from_chars(sec2.data(), sec2.data() + hy, std::get<2>(out));
+    std::from_chars(sec2.data() + hy + 1, sec2.data() + sec2.size(),
+                    std::get<3>(out));
+  }
+  return out;
+}
+
+long p1(const auto &input) {
+  long c{0};
+  for (const auto &l : input) {
+    auto [s1b, s1e, s2b, s2e] = parse(l);
+    c += ((s1b >= s2b && s1e <= s2e) || (s1b <= s2b && s1e >= s2e)) ? 1 : 0;
+  }
+  return c;
+}
+
+long p2(const auto &input) {
+  long c{0};
+  for (const auto &l : input) {
+    auto [s1b, s1e, s2b, s2e] = parse(l);
+    c += (s1e < s2b || s2e < s1b) ? 0 : 1;
+  }
+  return c;
+}
+} // namespace
+
+int main() {
+  const auto &input = gb::advent2021::readIn();
+  gb::advent2021::writeOut(std::to_string(p1(input)));
+  gb::advent2021::writeOut(std::to_string(p2(input)));
+}

cpp/common.h

@@ -1,6 +1,7 @@
 #include <algorithm>
 #include <bitset>
 #include <cctype>
+#include <charconv>
 #include <climits>
 #include <cmath>
 #include <cstdint>

cpp/meson.build

@@ -14,9 +14,9 @@ executable('3',
     '3.cpp',
     dependencies: [])
 
-# executable('4',
-#     '4.cpp',
-#     dependencies: [])
+executable('4',
+    '4.cpp',
+    dependencies: [])
 
 # executable('5',
 #     '5.cpp',