From 44d79ff3efaca242532e142f3796328918c1e942 Mon Sep 17 00:00:00 2001
From: Eric Mertens <emertens@gmail.com>
Date: Sun, 29 Dec 2024 14:48:07 -0600
Subject: [PATCH] 2024-19

---
 2024/19.cpp         | 62 +++++++++++++++++++++++++++++++++++++++++++++
 2024/CMakeLists.txt |  3 +++
 2 files changed, 65 insertions(+)
 create mode 100644 2024/19.cpp

diff --git a/2024/19.cpp b/2024/19.cpp
new file mode 100644
index 0000000..39b3d17
--- /dev/null
+++ b/2024/19.cpp
@@ -0,0 +1,62 @@
+#include <aocpp/Parsing.hpp>
+#include <aocpp/Startup.hpp>
+
+#include <boost/spirit/include/qi.hpp>
+#include <boost/fusion/include/std_tuple.hpp>
+
+#include <cstdint>
+#include <iostream>
+#include <string_view>
+#include <string>
+#include <tuple>
+#include <vector>
+
+namespace qi = boost::spirit::qi;
+
+using std::istream;
+using std::ostream;
+using std::size_t;
+using std::string_view;
+using std::string;
+using std::tuple;
+using std::uint64_t;
+using std::vector;
+
+namespace {
+
+auto ways(vector<string> const& towels, string const& design) -> uint64_t
+{
+  vector<uint64_t> counts(design.size() + 1);
+  counts[0] = 1;
+
+  for (size_t i = 0; i < design.size(); i++) {
+    auto const suffix = string_view{ begin(design) + i, end(design) };
+    for (auto && towel : towels) {
+      if (suffix.starts_with(towel)) {
+        counts[i + towel.size()] += counts[i];
+      }
+    }
+  }
+
+  return counts.back();
+}
+
+} // namespace
+
+auto Main(istream & in, ostream & out) -> void
+{
+  auto const [towels, designs] = 
+    aocpp::ParseSimple
+      <tuple<vector<string>, vector<string>>>
+      (in, +qi::alpha % ", " >> "\n\n" >> *(+qi::alpha >> "\n"));
+
+  uint64_t p1 = 0, p2 = 0;
+  for (auto && d : designs) {
+    auto const n = ways(towels, d);
+    if (n > 0) { p1++; }
+    p2 += n;
+  }
+
+  out << "Part 1: " << p1 << "\n"
+      << "Part 2: " << p2 << "\n";
+}
diff --git a/2024/CMakeLists.txt b/2024/CMakeLists.txt
index e4d52ec..866866d 100644
--- a/2024/CMakeLists.txt
+++ b/2024/CMakeLists.txt
@@ -4,5 +4,8 @@ target_link_libraries(2024_01 aocpp Boost::headers)
 add_executable(2024_07 07.cpp)
 target_link_libraries(2024_07 aocpp Boost::headers)
 
+add_executable(2024_19 19.cpp)
+target_link_libraries(2024_19 aocpp Boost::headers)
+
 add_executable(2024_22 22.cpp)
 target_link_libraries(2024_22 aocpp)