Add 2017 day 3 puzzles

2017/puzzle-03-01.cc

@@ -0,0 +1,46 @@
+#include <iostream>
+#include <string>
+
+template<typename T>
+auto sign(T i) -> decltype(i)
+{
+  if (i < 0) {
+    return -1;
+  }
+  if (i > 0) {
+    return 1;
+  }
+  return 0;
+}
+
+auto main() -> int
+{
+  std::string line;
+  if (!std::getline(std::cin, line)) {
+    std::cerr << "Broken line" << '\n';
+    return 1;
+  }
+
+  auto target{std::stoul(line)};
+  std::pair<int, int> dist{1, 0};
+  std::pair<int, int> pos{0, 0};
+  decltype(target) val{1};
+
+  while (val + std::abs(dist.first) + std::abs(dist.second) < target) {
+    val += std::abs(dist.first) + std::abs(dist.second);
+    pos = {pos.first + dist.first, pos.second + dist.second};
+    dist = {-dist.second, dist.first};
+    if (dist.first > 0) {
+      ++dist.first;
+    }
+    if (dist.first < 0) {
+      --dist.first;
+    }
+  }
+  auto delta{target - val};
+  pos = {pos.first + sign(dist.first) * delta, pos.second + sign(dist.second) * delta};
+
+  std::cout << "Pos = [" << pos.first << ", " << pos.second
+            << "], distance = " << std::abs(pos.first) + std::abs(pos.second) << '\n';
+  return 0;
+}