1 files changed, 44 insertions, 0 deletions
diff --git a/src/2019/day3/aoc.cpp b/src/2019/day3/aoc.cpp
index f0cbc1b..a81a29f 100644
--- a/src/2019/day3/aoc.cpp
+++ b/src/2019/day3/aoc.cpp
@@ -2,4 +2,48 @@
 
 namespace aoc2019 {
 
+bool cross(const wire::line& lh, const wire::line& lv, day3point* p) {
+  auto in_range = [](int x, int a, int b) {
+    int min = std::min(a, b);
+    int max = std::max(a, b);
+    return x >= min && x <= max;
+  };
+  bool b1 = in_range(lv.a.x, lh.a.x, lh.b.x);
+  bool b2 = in_range(lh.a.y, lv.a.y, lv.b.y);
+  if (b1 && b2) {
+    *p = {lv.a.x, lh.a.y};
+    return true;
+  }
+  return false;
 }
+
+void match(const std::vector<wire::line>& lhs, const std::vector<wire::line>& lvs, day3point* p) {
+  for (auto& lh : lhs) {
+    for (auto& lv : lvs) {
+      if (cross(lh, lv, p)) {
+        return;
+      }
+    }
+  }
+}
+
+int day3(line_view file) {
+  wire ws[2];
+  day3point mp{0, 0};
+  int i{0};
+  per_line(file, [&ws, &mp, &i](line_view lv) {
+    day3point cp{0, 0};
+    ws[i++].parse(lv, &cp, &mp);
+    return true;
+  });
+  ws[0].sort();
+  ws[1].sort();
+  day3point p1;
+  day3point p2;
+  match(ws[0].psh, ws[1].psv, &p1);
+  match(ws[1].psh, ws[0].psv, &p2);
+  day3point p = std::min(p1, p2);
+  return p.distance() ;
+}
+
+} // namespace aoc2019