aoc 2024, day 19

1 files changed, 115 insertions, 0 deletions

diff --git a/2024/src/day19.cpp b/2024/src/day19.cpp
new file mode 100644
index 0000000..43995b1
--- /dev/null
+++ b/2024/src/day19.cpp
@@ -0,0 +1,115 @@
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <numeric>
+#include <set>
+#include <string>
+#include <tuple>
+#include <vector>
+using namespace std;
+
+vector<string>
+split(string_view line, string_view delimiter)
+{
+        size_t pos_start = 0;
+        size_t pos_end   = 0;
+
+        vector<string> res;
+
+        while ( (pos_end = line.find(delimiter, pos_start)) != std::string::npos ) {
+                auto token = line.substr(pos_start, pos_end - pos_start);
+                pos_start  = pos_end + delimiter.length();
+
+                res.emplace_back(token);
+        }
+
+        res.emplace_back(line.substr(pos_start));
+        return res;
+}
+
+tuple<set<string>, vector<string>>
+read_file(string_view filename)
+{
+        fstream input{ filename };
+
+        vector<string> lines;
+        for ( string line; getline(input, line); ) {
+                lines.emplace_back(line);
+        }
+
+        const auto parts = split(lines[0], ", ");
+
+        return { { parts.begin(), parts.end() }, { lines.begin() + 2, lines.end() } };
+}
+
+void
+part1(const tuple<set<string>, vector<string>>& data)
+{
+        const auto& parts = get<0>(data);
+        const auto& lines = get<1>(data);
+
+        map<string, bool> cache;
+
+        function<bool(const string&)> match = [&](const string& line) {
+                if ( line.empty() ) {
+                        return true;
+                }
+
+                if ( cache.contains(line) ) {
+                        return cache.at(line);
+                }
+
+                for ( size_t i = 0; i != line.size(); ++i ) {
+                        if ( parts.contains(line.substr(0, i + 1)) ) {
+                                if ( match(line.substr(i + 1)) ) {
+                                        return cache[line] = true;
+                                }
+                        }
+                }
+
+                return cache[line] = false;
+        };
+
+        cout << ranges::count_if(lines, match) << endl;
+}
+
+void
+part2(const tuple<set<string>, vector<string>>& data)
+{
+        const auto& parts = get<0>(data);
+        const auto& lines = get<1>(data);
+
+        map<string, long> cache;
+
+        function<long(const string&)> match = [&](const string& line) -> long {
+                if ( line.empty() ) {
+                        return 1;
+                }
+
+                if ( cache.contains(line) ) {
+                        return cache.at(line);
+                }
+
+                long counter = 0;
+                for ( size_t i = 0; i != line.size(); ++i ) {
+                        auto lhs = line.substr(0, i + 1);
+                        auto rhs = line.substr(i + 1);
+
+                        if ( parts.contains(lhs) ) {
+                                counter += match(rhs);
+                        }
+                }
+
+                return cache[line] = counter;
+        };
+
+        cout << accumulate(lines.begin(), lines.end(), 0L, [&](auto init, const auto& line) { return init + match(line); }) << endl;
+}
+
+int
+main()
+{
+        const auto data = read_file("data/day19.txt");
+        part1(data);
+        part2(data);
+}