1 files changed, 104 insertions, 0 deletions

diff --git a/2017/src/day11.cpp b/2017/src/day11.cpp
new file mode 100644
index 0000000..ea945c1
--- /dev/null
+++ b/2017/src/day11.cpp
@@ -0,0 +1,104 @@
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <sstream>
+#include <string>
+#include <vector>
+
+// see: https://www.redblobgames.com/grids/hexagons/
+
+using namespace std;
+
+namespace {
+
+string
+read_file(const filesystem::path& filename)
+{
+        ifstream file{ filename };
+        string   line;
+        getline(file, line);
+        return line;
+}
+
+vector<string>
+split(const string& line)
+{
+        stringstream   strm{ line };
+        vector<string> data;
+
+        for ( string word; getline(strm, word, ','); ) {
+                data.emplace_back(word);
+        }
+
+        return data;
+}
+
+void
+part1(const vector<string>& steps)
+{
+        // string => (q, s, r)
+        map<string, tuple<int, int, int>> dirs{
+                { "n", { 0, 1, -1 } },
+                { "nw", { -1, 1, 0 } },
+                { "sw", { -1, 0, 1 } },
+                { "s", { 0, -1, 1 } },
+                { "se", { 1, -1, 0 } },
+                { "ne", { 1, 0, -1 } }
+        };
+
+        tuple<int, int, int> current = { 0, 0, 0 };
+        for ( const auto& step: steps ) {
+                const auto [dq, ds, dr] = dirs.at(step);
+
+                get<0>(current) += dq;
+                get<1>(current) += ds;
+                get<2>(current) += dr;
+        }
+
+        auto dist = (abs(get<0>(current)) + abs(get<1>(current)) + abs(get<2>(current))) / 2;
+
+        cout << "Part1: " << dist << '\n';
+}
+
+void
+part2(const vector<string>& steps)
+{
+        // string => (q, s, r)
+        map<string, tuple<int, int, int>> dirs{
+                { "n", { 0, 1, -1 } },
+                { "nw", { -1, 1, 0 } },
+                { "sw", { -1, 0, 1 } },
+                { "s", { 0, -1, 1 } },
+                { "se", { 1, -1, 0 } },
+                { "ne", { 1, 0, -1 } }
+        };
+
+        int max_dist = 0;
+
+        tuple<int, int, int> current = { 0, 0, 0 };
+        for ( const auto& step: steps ) {
+                const auto [dq, ds, dr] = dirs.at(step);
+
+                get<0>(current) += dq;
+                get<1>(current) += ds;
+                get<2>(current) += dr;
+
+                auto dist = (abs(get<0>(current)) + abs(get<1>(current)) + abs(get<2>(current))) / 2;
+
+                max_dist = max(max_dist, dist);
+        }
+
+        cout << "Part2: " << max_dist << '\n';
+}
+
+} // namespace
+
+int
+main()
+{
+        auto line  = read_file("data/day11.txt");
+        auto steps = split(line);
+        part1(steps);
+        part2(steps);
+}