1 files changed, 77 insertions, 0 deletions

diff --git a/2017/src/day13.cpp b/2017/src/day13.cpp
new file mode 100644
index 0000000..759f302
--- /dev/null
+++ b/2017/src/day13.cpp
@@ -0,0 +1,77 @@
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <tuple>
+#include <vector>
+
+using namespace std;
+
+namespace {
+
+vector<tuple<unsigned long, unsigned long>>
+read_file(const filesystem::path& filename)
+{
+        ifstream      file{ filename };
+        unsigned long depth = 0;
+        unsigned long range = 0;
+        char          colon = 0;
+
+        vector<tuple<unsigned long, unsigned long>> data;
+
+        while ( file >> depth >> colon >> range ) {
+                data.emplace_back(depth, range);
+        }
+
+        return data;
+}
+
+template<typename T>
+T
+get_pos(T depth, T range, T time)
+{
+        const auto period    = 2 * (range - 1);
+        const auto remainder = (depth + time) % period;
+        return remainder < range ? remainder : period - remainder;
+}
+
+void
+part1(const vector<tuple<unsigned long, unsigned long>>& data)
+{
+        unsigned long sum = 0;
+        for ( const auto [depth, range]: data ) {
+                if ( get_pos(depth, range, 0UL) == 0 ) {
+                        sum += depth * range;
+                }
+        }
+        cout << "Part1: " << sum << '\n';
+}
+
+void
+part2(const vector<tuple<unsigned long, unsigned long>>& data)
+{
+        for ( unsigned long delay = 0;; ++delay ) {
+                bool pass = true;
+
+                for ( const auto [depth, range]: data ) {
+                        if ( get_pos(depth, range, delay) == 0 ) {
+                                pass = false;
+                                break;
+                        }
+                }
+
+                if ( pass ) {
+                        cout << "Part2: " << delay << '\n';
+                        return;
+                }
+        }
+}
+
+} // namespace
+
+int
+main()
+{
+        auto data = read_file("data/day13.txt");
+        part1(data);
+        part2(data);
+}