2023: day 16 part 2 complete (but slower than I'd like)

yut23 · Dec 18, 2023 · 65a26a0 · 65a26a0
1 parent 39a83f8
commit 65a26a0
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Showing 2 changed files with 46 additions and 13 deletions.
diff --git a/2023/src/day16.cpp b/2023/src/day16.cpp
@@ -18,13 +18,46 @@ int main(int argc, char **argv) {
         std::cerr << grid << "\n";
     }
 
-    grid.send_beam();
-    if constexpr (aoc::DEBUG) {
-        grid.print_energized(std::cerr);
-        std::cerr << "\n";
+    // TODO: optimize this
+    // some sort of DP should work, but loops will need special handling
+
+    int max_energized = 0;
+    aoc::Pos pos(0, 0);
+    for (pos.y = 0; pos.y < grid.height(); ++pos.y) {
+        for (pos.x = 0; pos.x < grid.width(); pos.x += grid.width() - 1) {
+            aoc::AbsDirection dir =
+                pos.x == 0 ? aoc::AbsDirection::east : aoc::AbsDirection::west;
+            grid.send_beam(pos, dir);
+            int count = grid.count_energized();
+            if (pos.x == 0 && pos.y == 0) {
+                // part 1
+                if constexpr (aoc::DEBUG) {
+                    grid.print_energized(std::cerr);
+                    std::cerr << "\n";
+                }
+                std::cout << count << "\n";
+            }
+            if (max_energized < count) {
+                max_energized = count;
+            }
+            grid.clear_energized();
+        }
     }
-    int part_1 = grid.count_energized();
-    std::cout << part_1 << "\n";
+
+    for (pos.x = 0; pos.x < grid.width(); ++pos.x) {
+        for (pos.y = 0; pos.y < grid.height(); pos.y += grid.height() - 1) {
+            aoc::AbsDirection dir = pos.y == 0 ? aoc::AbsDirection::south
+                                               : aoc::AbsDirection::north;
+            grid.send_beam(pos, dir);
+            int count = grid.count_energized();
+            if (max_energized < count) {
+                max_energized = count;
+            }
+            grid.clear_energized();
+        }
+    }
+
+    std::cout << max_energized << "\n";
 
     return 0;
 }
diff --git a/2023/src/day16.hpp b/2023/src/day16.hpp
@@ -98,23 +98,26 @@ class Grid {
     void send_beam_helper(Pos pos, AbsDirection dir, visit_cache_t &seen);
 
   public:
-    void send_beam();
+    void send_beam(Pos pos, AbsDirection dir);
     void clear_energized();
     int count_energized() const;
 
+    int width() const { return tiles[0].size(); }
+    int height() const { return tiles.size(); }
+
     static Grid read(std::istream &);
 
     void print_energized(std::ostream &os) const;
     friend std::ostream &operator<<(std::ostream &, const Grid &);
 };
 
-void Grid::send_beam() {
+void Grid::send_beam(Pos pos, AbsDirection dir) {
     visit_cache_t seen;
-    send_beam_helper(Pos(0, 0), AbsDirection::east, seen);
+    send_beam_helper(pos, dir, seen);
 }
 
 void Grid::send_beam_helper(Pos pos, AbsDirection dir, visit_cache_t &seen) {
-    while (true) {
+    while (in_bounds(pos)) {
         auto key = std::make_pair(pos, dir);
         if (seen.contains(key)) {
             return;
@@ -130,9 +133,6 @@ void Grid::send_beam_helper(Pos pos, AbsDirection dir, visit_cache_t &seen) {
         }
         dir = new_dirs[0];
         pos += Delta(dir, true);
-        if (!in_bounds(pos)) {
-            break;
-        }
     }
 }