Add 2017 day 3 puzzles

2017/puzzle-03-02.cc

@@ -0,0 +1,71 @@
+#include <iostream>
+#include <map>
+#include <string>
+
+using Int = long;
+using Coord = std::pair<Int, Int>;
+using ValueMap = std::map<Coord, Int>;
+
+template<typename T>
+auto sign(T i) -> decltype(i)
+{
+  if (i < 0) {
+    return -1;
+  }
+  if (i > 0) {
+    return 1;
+  }
+  return 0;
+}
+
+auto value(ValueMap const& map, Coord const& coord) -> Int
+{
+  auto result{0};
+  for (auto x{coord.first - 1}; x < coord.first + 2; ++x) {
+    for (auto y{coord.second - 1}; y < coord.second + 2; ++y) {
+      if (x == coord.first && y == coord.second) {
+        continue;
+      }
+      auto it{map.find(Coord{x, y})};
+      if (it != map.end()) {
+        result += it->second;
+      }
+    }
+  }
+
+  return result;
+}
+
+auto main() -> int
+{
+  std::string line;
+  if (!std::getline(std::cin, line)) {
+    std::cerr << "Broken line" << '\n';
+    return 1;
+  }
+
+  auto target{std::stol(line)};
+  Coord dir{1, 0};
+  Coord pos{0, 0};
+  Int count{1};
+  Int count_reset{1};
+  ValueMap map;
+  map.insert({pos, 1});
+
+  while (true) {
+    while (count-- != 0) {
+      pos = {pos.first + dir.first, pos.second + dir.second};
+      auto val{value(map, pos)};
+      if (val > target) {
+        std::cout << val << '\n';
+        return 0;
+      }
+      map.insert({pos, val});
+    }
+    dir = {-dir.second, dir.first};
+    if (dir.first != 0) {
+      ++count_reset;
+    }
+    count = count_reset;
+  }
+}