2 files changed, 127 insertions, 1 deletions
diff --git a/src/2018/day6/aoc.cpp b/src/2018/day6/aoc.cpp
index 585f144..5350b0e 100644
--- a/src/2018/day6/aoc.cpp
+++ b/src/2018/day6/aoc.cpp
@@ -1,5 +1,35 @@
 #include "aoc.h"
+#include <algorithm>
 
 namespace aoc2018 {
 
+int day6(line_view file) {
+  std::vector<coordinate> cs;
+  int maxx{INT32_MIN};
+  int maxy{INT32_MIN};
+
+  per_line(file, [&cs, &maxx, &maxy](line_view lv) {
+    coordinate c(lv);
+    cs.push_back(c);
+    maxx = std::max(maxx, c.x);
+    maxy = std::max(maxx, c.y);
+    return true;
+  });
+
+  std::sort(cs.begin(), cs.end());
+  space_board b{maxx + 1, maxy + 1};
+
+  for (size_t i = 0; i < cs.size(); i++) {
+    coordinate& c = cs[i];
+    auto& p = b.ps[c.y * b.rows + c.x];
+    p.id = i;
+    p.distance = 0;
+
+    std::vector<int> total = {0};
+    c.traverse([&total, &b, &c](int lap, int dir, coordinate x) { return true; },
+               [&total]() { return total[total.size() - 1] == 0; });
+  }
+  return 0;
 }
+
+} // namespace aoc2018
diff --git a/src/2018/day6/aoc.h b/src/2018/day6/aoc.h
index 4bfdbf3..5d27936 100644
--- a/src/2018/day6/aoc.h
+++ b/src/2018/day6/aoc.h
@@ -1,6 +1,102 @@
 #pragma once
 #include "common.h"
+#include <math.h>
+#include <utility>
+#include <vector>
 
 namespace aoc2018 {
 
-}
+struct coordinate {
+  int x = 0;
+  int y = 0;
+
+  coordinate(int xx, int yy) : x(xx), y(yy) {}
+  coordinate(line_view lv) {
+    const char* p = lv.line;
+    int* d[] = {&x, &y};
+    int i{0};
+    while (p < lv.line + lv.length) {
+      if (*p >= '0' && *p <= '9') {
+        get_number(&p, d[i++]);
+      }
+      p++;
+    }
+  }
+
+  void get_number(const char** pp, int* d) {
+    const char* p = *pp;
+    *d = 0;
+    while (*p >= '0' && *p <= '9') {
+      *d = *d * 10 + *p - '0';
+      p++;
+    }
+    *pp = p;
+  }
+
+  int distance(coordinate c = coordinate{0, 0}) const noexcept { return std::abs(x - c.x) + std::abs(y - c.y); }
+  coordinate right(int d) { return {x + d, y}; }
+  coordinate up(int d) { return {x, y - d}; }
+  coordinate left(int d) { return {x - d, y}; }
+  coordinate down(int d) { return {x, y + d}; }
+  typedef coordinate (coordinate::*move)(int);
+
+  bool operator<(const coordinate& c) const noexcept {
+    int d1 = distance();
+    int d2 = c.distance();
+    return d1 < d2 ? true : (d1 > d2 ? false : (x < c.x ? true : (x > c.x ? false : y < c.y)));
+  }
+
+  template <typename F, typename G, typename... Args>
+  void traverse(F&& f, G&& g, Args&&... args) const noexcept {
+    // right, up, left, down
+    auto next = [](int i, coordinate c) -> coordinate {
+      move fs[] = {&coordinate::right, &coordinate::up, &coordinate::left, &coordinate::down};
+      return (c.*(fs[i]))(1);
+    };
+    int steps[] = {1, 1, 2, 2};
+    int i{0};
+    coordinate c = *this;
+    bool stop{false};
+    while (!stop) {
+      int s = i % 4;
+      for (int x = 0; x < steps[s] && !stop; x++) {
+        c = next(s, c);
+        stop = !f(i / 4, s, c, std::forward<Args>(args)...);
+      }
+      steps[s] += 2;
+      i++;
+      stop = stop || ((i % 4 == 0) && g());
+    }
+  }
+};
+
+struct space_board {
+  // -1 no one
+  // -2 same distance
+  struct point {
+    int id;
+    int distance;
+  };
+
+  int rows;
+  int cols;
+  std::vector<point> ps;
+  space_board(int x, int y) : rows(x), cols(y), ps(x * y, {-1, INT32_MAX}){};
+
+  void count(std::vector<int>& area) {
+    for (int y = 0; y < cols; y++) {
+      for (int x = 0; x < rows; x++) {
+        auto p = ps[y * rows + x];
+        if (x == 0 || y == 0 || x == rows - 1 || y == cols - 1) {
+          area[p.id] = INT32_MAX;
+        } else {
+          area[p.id] += 1;
+        }
+      }
+    }
+  }
+};
+
+int day6(line_view);
+
+} // namespace aoc2018