1 files changed, 70 insertions, 0 deletions

diff --git a/2023/08/src/part1.cpp b/2023/08/src/part1.cpp
new file mode 100644
index 0000000..9585536
--- /dev/null
+++ b/2023/08/src/part1.cpp
@@ -0,0 +1,70 @@
+#include <iostream>
+#include <fstream>
+#include <sstream>
+#include <unordered_map>
+#include <vector>
+
+#include "util.h"
+
+using Moves = std::vector<bool>;
+using Map = std::unordered_map<int,std::pair<int,int>>;
+
+constexpr char EQUAL[] = "=";
+
+int encode(std::string str)
+{
+    int res{};
+    for (unsigned char c : str)
+    {
+        if ('A' <= c and c <= 'Z')
+        {
+            res *= 1 + 'Z' - 'A';
+            res += c - 'A';
+        }
+    }
+    return res;
+}
+
+std::pair<Moves,Map> parse(const char* path)
+{
+    Map map{};
+    Moves moves{};
+
+    std::ifstream input{ path };
+    if (input.is_open())
+    {
+        std::string line;
+        std::getline(input,line);
+
+        moves.resize(line.size());
+        std::transform(line.cbegin(), line.cend(),
+            moves.begin(), [](unsigned char c) { return c == 'L'; });
+
+        std::string from, tol, tor;
+        while (not std::getline(input,line).eof())
+        {
+            if (line.empty()) continue;
+
+            std::istringstream in{ line };
+            in >> from >> util::skip<EQUAL> >> tol >> tor;
+            map.insert({ encode(from), { encode(tol), encode(tor) } });
+        }
+    }
+    input.close();
+
+    return { std::move(moves), std::move(map) };
+}
+
+int main(int argc, char* argv[])
+{
+    int answer{};
+
+    auto [moves, map] = parse(argv[1]);
+
+    for (int pos = encode("AAA");
+         pos != encode("ZZZ");
+         pos = moves[answer++ % moves.size()] ? map[pos].first : map[pos].second);
+
+    std::cout << answer << std::endl;
+    return 0;
+}