1 files changed, 97 insertions, 0 deletions

diff --git a/2017/src/day19.cpp b/2017/src/day19.cpp
new file mode 100644
index 0000000..470bb4f
--- /dev/null
+++ b/2017/src/day19.cpp
@@ -0,0 +1,97 @@
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <string>
+#include <tuple>
+
+using namespace std;
+
+namespace {
+
+using dir_type    = tuple<size_t, size_t>;
+using pos_type    = tuple<size_t, size_t>;
+using puzzle_type = map<pos_type, char>;
+
+puzzle_type
+read_file(const filesystem::path& filename)
+{
+        ifstream    file{ filename };
+        puzzle_type data;
+
+        size_t row = 0;
+        for ( string line; getline(file, line); ) {
+                for ( size_t col = 0; col != line.size(); ++col ) {
+                        if ( line.at(col) != ' ' ) {
+                                data.emplace(pos_type{ col, row }, line.at(col));
+                        }
+                }
+                ++row;
+        }
+
+        return data;
+}
+
+pos_type
+find_start(const puzzle_type& puzzle)
+{
+        for ( size_t col = 0;; ++col ) {
+                const pos_type pos{ col, 0 };
+                if ( puzzle.contains(pos) && puzzle.at(pos) == '|' ) {
+                        return pos;
+                }
+        }
+}
+
+void
+solve(const puzzle_type& puzzle)
+{
+        string result;
+        size_t steps = 0;
+
+        pos_type pos = find_start(puzzle);
+        dir_type dir{ 0, 1 };
+
+        while ( puzzle.contains(pos) ) {
+                auto chr = puzzle.at(pos);
+
+                if ( chr >= 'A' && chr <= 'Z' ) {
+                        result += chr;
+                }
+                else if ( chr == '+' ) {
+                        auto [dx, dy] = dir;
+                        auto left     = dir_type{ -dy, dx };
+                        auto right    = dir_type{ dy, -dx };
+
+                        pos_type next_left  = { get<0>(pos) + get<0>(left), get<1>(pos) + get<1>(left) };
+                        pos_type next_right = { get<0>(pos) + get<0>(right), get<1>(pos) + get<1>(right) };
+
+                        if ( puzzle.contains(next_left) ) {
+                                dir = left;
+                        }
+                        else if ( puzzle.contains(next_right) ) {
+                                dir = right;
+                        }
+                        else {
+                                cerr << "Error!\n";
+                                return;
+                        }
+                }
+
+                get<0>(pos) += get<0>(dir);
+                get<1>(pos) += get<1>(dir);
+                ++steps;
+        }
+
+        cout << "Part1: " << result << '\n';
+        cout << "Part2: " << steps << '\n';
+}
+
+} // namespace
+
+int
+main()
+{
+        auto puzzle = read_file("data/day19.txt");
+        solve(puzzle);
+}