3 files changed, 63 insertions, 7 deletions

diff --git a/src/2016/day1/aoc.cpp b/src/2016/day1/aoc.cpp
index 2711d8f..8f79ece 100644
--- a/src/2016/day1/aoc.cpp
+++ b/src/2016/day1/aoc.cpp
@@ -17,10 +17,13 @@ instruction parse_day1(const char** pp) {
   return i;
 }
 
-int day1(line_view file) {
+std::pair<int, int> day1(line_view file) {
   position x{position::north, 0, 0};
   std::vector<instruction> is;
 
+  bool found = false;
+  position first;
+
   const char* p1 = file.line;
   const char* p2 = file.line + file.length;
   while (p1 < p2) {
@@ -30,8 +33,8 @@ int day1(line_view file) {
       p1++;
     }
   }
-  position n = x.move(is);
-  return x.blocks(n);
+  position n = x.move(is, &first, &found);
+  return {x.blocks(n), x.blocks(first)};
 }
 
 } // namespace aoc2016
diff --git a/src/2016/day1/aoc.h b/src/2016/day1/aoc.h
index abcafe0..b6e556e 100644
--- a/src/2016/day1/aoc.h
+++ b/src/2016/day1/aoc.h
@@ -2,6 +2,7 @@
 #include "common.h"
 #include <algorithm>
 #include <math.h>
+#include <set>
 #include <vector>
 
 namespace aoc2016 {
@@ -25,6 +26,7 @@ struct position {
   int x;
   int y;
 
+  bool operator<(const position& p) const noexcept { return x < p.x ? true : (x > p.x ? false : y < p.y); }
   int blocks(position p) const noexcept { return abs(p.x - x) + abs(p.y - y); }
 
   position move(instruction i) const noexcept {
@@ -52,13 +54,64 @@ struct position {
     return next;
   }
 
-  position move(const std::vector<instruction>& is) const noexcept {
+  std::vector<position> line(position p1, position p2) const noexcept {
+    std::vector<position> ps;
+    auto copyx = [&p1, &p2, &ps](int x) {
+      if (x > 0) {
+        for (int i = p1.x; i < p2.x; i++) {
+          ps.push_back({p2.b, i, p1.y});
+        }
+      }
+      if (x < 0) {
+        for (int i = p1.x; i > p2.x; i--) {
+          ps.push_back({p2.b, i, p1.y});
+        }
+      }
+    };
+    auto copyy = [&p1, &p2, &ps](int y) {
+      if (y > 0) {
+        for (int i = p1.y; i < p2.y; i++) {
+          ps.push_back({p2.b, p1.x, i});
+        }
+      }
+      if (y < 0) {
+        for (int i = p1.y; i > p2.y; i--) {
+          ps.push_back({p2.b, p1.x, i});
+        }
+      }
+    };
+    copyx(p2.x - p1.x);
+    copyy(p2.y - p1.y);
+    return ps;
+  }
+
+  void cross(position p1, position p2, position* first, bool* found) const noexcept {
+    static std::set<position> ps = {};
+    if (!(*found)) {
+      auto v = line(p1, p2);
+      for (size_t i = 0; i < v.size(); i++) {
+        // printf("%d %d %d\n", int(v[i].b), v[i].x, v[i].y);
+        auto p = ps.insert(v[i]);
+        if (!p.second) {
+          *found = true;
+          *first = *p.first;
+          return;
+        }
+      }
+    }
+  }
+
+  position move(const std::vector<instruction>& is, position* first, bool* found) const noexcept {
     position next = *this;
-    std::for_each(is.begin(), is.end(), [&next](const instruction& i) { next = next.move(i); });
+    std::for_each(is.begin(), is.end(), [&next, first, found, this](const instruction& i) {
+      position prev = next;
+      next = next.move(i);
+      cross(prev, next, first, found);
+    });
     return next;
   }
 };
 
-int day1(line_view);
+std::pair<int, int> day1(line_view);
 
 } // namespace aoc2016
diff --git a/src/2019/day1/aoc.h b/src/2019/day1/aoc.h
index 95823fe..959d6d8 100644
--- a/src/2019/day1/aoc.h
+++ b/src/2019/day1/aoc.h
@@ -1,6 +1,6 @@
 #pragma once
 #include "common.h"
 
-namespace aoc2016 {
+namespace aoc2019 {
 
 }