2017-12

lib/include/aocpp/Hex.hpp

@@ -0,0 +1,57 @@
+#ifndef AOCPP_HEX_HPP_
+#define AOCPP_HEX_HPP_
+
+#include <numeric>
+#include <cstdint>
+
+namespace aocpp {
+/*
+  \ n  /
+nw +--+ ne
+  /    \
+-+      +-
+  \    /
+sw +--+ se
+  / s  \
+*/
+
+struct Hex {
+  std::int64_t q, r, s;
+};
+
+constexpr Hex HEX_N  {  0, -1,  1 };
+constexpr Hex HEX_NE {  1, -1,  0 };
+constexpr Hex HEX_SE {  1,  0, -1 };
+constexpr Hex HEX_S  {  0,  1, -1 };
+constexpr Hex HEX_SW { -1,  1,  0 };
+constexpr Hex HEX_NW { -1,  0,  1 };
+
+auto operator+(Hex const& a, Hex const& b) -> Hex {
+  return {a.q + b.q, a.r + b.r, a.s + b.s };
+}
+
+auto operator+=(Hex & a, Hex const& b) -> Hex & {
+  a.q += b.q; a.r += b.r; a.s += b.s;
+  return a;
+}
+
+auto operator-(Hex const& a, Hex const& b) -> Hex {
+  return {a.q - b.q, a.r - b.r, a.s - b.s };
+}
+
+auto operator-=(Hex & a, Hex const& b) -> Hex & {
+  a.q -= b.q; a.r -= b.r; a.s -= b.s;
+  return a;
+}
+
+auto operator-(Hex const& a) -> Hex {
+  return {-a.q, -a.r, -a.s };
+}
+
+auto hex_distance(Hex hex) -> std::int64_t {
+  return (std::abs(hex.q) + std::abs(hex.r) + std::abs(hex.s)) / 2;
+}
+
+} // namespace
+
+#endif