1 files changed, 97 insertions, 0 deletions
diff --git a/src/2019/day10/aoc.h b/src/2019/day10/aoc.h
index 9951322..d3cdb76 100644
--- a/src/2019/day10/aoc.h
+++ b/src/2019/day10/aoc.h
@@ -1,7 +1,104 @@
 #pragma once
 #include "common.h"
+#include <math.h>
 
 namespace aoc2019 {
 
+struct belt {
+  static constexpr int grid = 34;
+
+  struct distance {
+    int dx;
+    int dy;
+  };
+
+  struct pos {
+    int x;
+    int y;
+
+    friend bool operator==(const pos &p1, const pos &p2) {
+      return p1.x == p2.x && p1.y == p2.y;
+    }
+  };
+
+  char map[grid * grid] = {0};
+
+  belt(const belt& b) {
+    memcpy(map, b.map, grid * grid);
+  }
+
+  belt() {}
+
+  char& get(int x, int y) {
+    return map[y * grid + x];
+  }
+
+  char& get(pos p) {
+    return get(p.x, p.y);
+  }
+
+  void load(line_view lv, int row) {
+    const char* p = lv.line;
+    for (int i = 0; i < grid; i++) {
+      get(i, row) = *(p + i);
+    }
+  }
+
+  distance diff(pos px, pos p) const noexcept {
+    auto d = distance{px.x - p.x, px.y - p.y};
+    int g = gcd(std::abs(d.dx), std::abs(d.dy));
+    return distance {d.dx / g, d.dy / g};
+  }
+
+  bool valid (pos p) const noexcept {
+    return p.x >= 0 && p.x < grid && p.y >= 0 && p.y < grid;
+  }
+
+  pos next(pos p, distance d) const noexcept {
+    return pos{p.x + d.dx, p.y + d.dy};
+  }
+
+  bool blocked(pos p, pos m) {
+    auto d = diff(p, m);
+    auto n = next(m, d);
+    while (valid(n) && !(n == p)) {
+      if (get(n) == '#') {
+        return true;
+      }
+      n = next(n, d);
+    }
+    return false;
+  }
+
+  template<typename F, typename... Args>
+  void iterate(F&& f, Args&&... args) {
+    for(int y = 0; y < grid; y++) {
+      for (int x = 0; x < grid; x++) {
+        f(pos{x, y}, std::forward(args)...);
+      }
+    }
+  }
+
+  void print() {
+    iterate([this](pos p){
+      printf("%c", get(p));
+      if (p.x == grid - 1) {
+        printf("\n");
+      }
+    });
+    printf("\n");
+  }
+
+  void count(pos m, int* c) {
+    iterate([this, &m, &c](pos p){
+      if (get(p) == '#' && !(p == m)) {
+        if (!blocked(p, m)) {
+          *c += 1;
+        }  
+      }
+    });
+  }
+};
+
 std::pair<int, int> day10(line_view);
 }