1 files changed, 115 insertions, 0 deletions

diff --git a/2017/src/day12.cpp b/2017/src/day12.cpp
new file mode 100644
index 0000000..66bf186
--- /dev/null
+++ b/2017/src/day12.cpp
@@ -0,0 +1,115 @@
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <queue>
+#include <set>
+#include <string>
+#include <vector>
+
+using namespace std;
+
+namespace {
+
+using graph_type = map<int, set<int>>;
+
+vector<int>
+split_to_int(const string& line, const string& delimiters)
+{
+        vector<int> result;
+
+        size_t start = 0;
+        size_t end   = 0;
+
+        while ( (end = line.find_first_of(delimiters, start)) != string::npos ) {
+                if ( end != start ) {
+                        result.emplace_back(stoi(line.substr(start, end - start)));
+                }
+
+                start = end + 1;
+        }
+
+        if ( start != line.size() ) {
+                result.emplace_back(stoi(line.substr(start)));
+        }
+
+        return result;
+}
+
+graph_type
+read_lines(const filesystem::path& filename)
+{
+        ifstream   file{ filename };
+        graph_type result;
+
+        for ( string line; getline(file, line); ) {
+                auto parts = split_to_int(line, "<-> ,");
+
+                for ( size_t i = 1; i < parts.size(); ++i ) {
+                        result[parts[0]].insert(parts[i]);
+                        result[parts[i]].insert(parts[0]);
+                }
+        }
+
+        return result;
+}
+
+void
+bfs_mark(const graph_type& graph, int start, set<int>& seen)
+{
+        queue<int> queue;
+
+        queue.emplace(start);
+        seen.emplace(start);
+
+        while ( !queue.empty() ) {
+                int prg = queue.front();
+                queue.pop();
+
+                for ( auto link: graph.at(prg) ) {
+                        if ( !seen.contains(link) ) {
+                                queue.emplace(link);
+                                seen.emplace(link);
+                        }
+                }
+        }
+}
+
+void
+part1(const graph_type& graph)
+{
+        set<int> seen;
+
+        bfs_mark(graph, 0, seen);
+
+        cout << "Part1: " << seen.size() << '\n';
+}
+
+void
+part2(const graph_type& graph)
+{
+        set<int> seen;
+
+        int count = 0;
+
+        for ( const auto& [i, _]: graph ) {
+                if ( seen.contains(i) ) {
+                        continue;
+                }
+
+                ++count;
+
+                bfs_mark(graph, i, seen);
+        }
+        cout << "Part2: " << count << '\n';
+}
+
+} // namespace
+
+int
+main()
+{
+        auto data = read_lines("data/day12.txt");
+        part1(data);
+        part2(data);
+}