1 files changed, 61 insertions, 0 deletions
diff --git a/src/2015/day3/aoc.cpp b/src/2015/day3/aoc.cpp
new file mode 100644
index 0000000..8dcf3c3
--- /dev/null
+++ b/src/2015/day3/aoc.cpp
@@ -0,0 +1,61 @@
+#include "aoc.h"
+#include <map>
+
+namespace aoc2015 {
+
+house move_day3(house h, dir d) {
+  house n = h;
+  switch (d) {
+  case dir::up:
+    n.y += 1;
+    break;
+  case dir::down:
+    n.y -= 1;
+    break;
+  case dir::left:
+    n.x -= 1;
+    break;
+  case dir::right:
+    n.x += 1;
+    break;
+  }
+  return n;
+}
+
+std::pair<size_t, size_t> day3(line_view lv) {
+  house h{0, 0};
+  house h1{0, 0};
+  house h2{0, 0};
+  std::map<house, size_t> m1{{h, 1}};
+  std::map<house, size_t> m2{{h, 1}};
+  house* hs[] = {&h1, &h2};
+
+  for (size_t i = 0; i < lv.length; i++) {
+    int x = i % 2;
+    switch (lv.line[i]) {
+    case '^':
+      h = move_day3(h, dir::up);
+      *hs[x] = move_day3(*hs[x], dir::up);
+      break;
+    case 'v':
+      h = move_day3(h, dir::down);
+      *hs[x] = move_day3(*hs[x], dir::down);
+      break;
+    case '>':
+      h = move_day3(h, dir::right);
+      *hs[x] = move_day3(*hs[x], dir::right);
+      break;
+    case '<':
+      h = move_day3(h, dir::left);
+      *hs[x] = move_day3(*hs[x], dir::left);
+      break;
+    default:
+      break;
+    }
+    m1.insert({h, 1});
+    m2.insert({*hs[x], 1});
+  }
+  return {m1.size(), m2.size()};
+}
+
+} // namespace aoc2015