Add 2016 day 17 puzzles

2016/puzzle-17-01.CMakeLists.txt

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+find_package(OpenSSL REQUIRED)
+target_link_libraries("${puzzle_name}" OpenSSL::SSL)

2016/puzzle-17-01.cc

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+//
+// Created by Matthew Gretton-Dann on 06/12/2021.
+//
+
+#include <array>
+#include <iostream>
+#include <set>
+#include <string>
+#include <utility>
+
+#include <openssl/evp.h>
+
+using MD5Digest = std::array<unsigned char, EVP_MAX_MD_SIZE>;
+
+enum Directions { none = 0x0, up = 0x1, down = 0x2, left = 0x4, right = 0x8 };
+auto md5_directions(std::string const& s) -> Directions
+{
+  MD5Digest digest;
+  EVP_MD const* md{EVP_md5()};
+  unsigned int md_len{0};
+
+  EVP_MD_CTX* md_context{EVP_MD_CTX_new()};
+  assert(md_context != nullptr);
+  EVP_DigestInit_ex2(md_context, md, nullptr);
+  EVP_DigestUpdate(md_context, s.data(), s.length());
+  EVP_DigestFinal_ex(md_context, digest.data(), &md_len);
+  Directions d{Directions::none};
+  if (((digest[0] & 0xf0) >> 4) > 0xa) {
+    d = static_cast<Directions>(d | Directions::up);
+  }
+  if ((digest[0] & 0xf) > 0xa) {
+    d = static_cast<Directions>(d | Directions::down);
+  }
+  if (((digest[1] & 0xf0) >> 4) > 0xa) {
+    d = static_cast<Directions>(d | Directions::left);
+  }
+  if ((digest[1] & 0xf) > 0xa) {
+    d = static_cast<Directions>(d | Directions::right);
+  }
+  return d;
+}
+
+struct Node
+{
+  explicit Node(std::string s) : str_(std::move(s)) {}
+
+  auto operator==(Node const& rhs) const noexcept -> bool { return str_ == rhs.str_; }
+
+  auto operator<(Node const& rhs) const noexcept -> bool
+  {
+    return str_.size() < rhs.str_.size() || (str_.size() == rhs.str_.size() && str_ < rhs.str_);
+  }
+
+  [[nodiscard]] auto str() const -> std::string const& { return str_; }
+  [[nodiscard]] auto x() const noexcept -> unsigned { return x_; }
+  [[nodiscard]] auto y() const noexcept -> unsigned { return y_; }
+
+  template<typename T>
+  void insert_moves(T inserter) const
+  {
+    Directions d{md5_directions(str_)};
+    if (x_ > 0 && (d & Directions::left) != Directions::none) {
+      *inserter++ = Node{str_ + 'L', x_ - 1, y_};
+    }
+    if (y_ > 0 && (d & Directions::up) != Directions::none) {
+      *inserter++ = Node{str_ + 'U', x_, y_ - 1};
+    }
+    if (x_ < 3 && (d & Directions::right) != Directions::none) {
+      *inserter++ = Node{str_ + 'R', x_ + 1, y_};
+    }
+    if (y_ < 3 && (d & Directions::down) != Directions::none) {
+      *inserter++ = Node{str_ + 'D', x_, y_ + 1};
+    }
+  }
+
+private:
+  Node(std::string s, unsigned x, unsigned y) : str_(std::move(s)), x_(x), y_(y) {}
+
+  std::string str_;
+  unsigned x_{0};
+  unsigned y_{0};
+};
+
+auto main() -> int
+{
+  std::string line;
+  if (!std::getline(std::cin, line)) {
+    std::cerr << "Failed to read line\n";
+    return 1;
+  }
+
+  Node initial_state{line};
+
+  std::set<Node> visited;
+  std::set<Node> to_visit;
+  to_visit.insert(initial_state);
+
+  while (!to_visit.empty()) {
+    auto it{to_visit.begin()};
+    Node n{*it};
+    to_visit.erase(it);
+    visited.insert(n);
+    if (n.x() == 3 && n.y() == 3) {
+      std::cout << "Movements " << n.str().substr(line.size()) << '\n';
+      return 0;
+    }
+    else {
+      n.insert_moves(std::inserter(to_visit, to_visit.end()));
+    }
+  }
+
+  std::cerr << "No solution.\n";
+  return 1;
+}

2016/puzzle-17-02.CMakeLists.txt

@@ -0,0 +1,2 @@
+find_package(OpenSSL REQUIRED)
+target_link_libraries("${puzzle_name}" OpenSSL::SSL)

2016/puzzle-17-02.cc

@@ -0,0 +1,117 @@
+//
+// Created by Matthew Gretton-Dann on 06/12/2021.
+//
+
+#include <array>
+#include <iostream>
+#include <set>
+#include <string>
+#include <utility>
+
+#include <openssl/evp.h>
+
+using MD5Digest = std::array<unsigned char, EVP_MAX_MD_SIZE>;
+
+enum Directions { none = 0x0, up = 0x1, down = 0x2, left = 0x4, right = 0x8 };
+auto md5_directions(std::string const& s) -> Directions
+{
+  MD5Digest digest;
+  EVP_MD const* md{EVP_md5()};
+  unsigned int md_len{0};
+
+  EVP_MD_CTX* md_context{EVP_MD_CTX_new()};
+  assert(md_context != nullptr);
+  EVP_DigestInit_ex2(md_context, md, nullptr);
+  EVP_DigestUpdate(md_context, s.data(), s.length());
+  EVP_DigestFinal_ex(md_context, digest.data(), &md_len);
+  Directions d{Directions::none};
+  if (((digest[0] & 0xf0) >> 4) > 0xa) {
+    d = static_cast<Directions>(d | Directions::up);
+  }
+  if ((digest[0] & 0xf) > 0xa) {
+    d = static_cast<Directions>(d | Directions::down);
+  }
+  if (((digest[1] & 0xf0) >> 4) > 0xa) {
+    d = static_cast<Directions>(d | Directions::left);
+  }
+  if ((digest[1] & 0xf) > 0xa) {
+    d = static_cast<Directions>(d | Directions::right);
+  }
+  return d;
+}
+
+struct Node
+{
+  explicit Node(std::string s) : str_(std::move(s)) {}
+
+  auto operator==(Node const& rhs) const noexcept -> bool { return str_ == rhs.str_; }
+
+  auto operator<(Node const& rhs) const noexcept -> bool
+  {
+    return str_.size() < rhs.str_.size() || (str_.size() == rhs.str_.size() && str_ < rhs.str_);
+  }
+
+  [[nodiscard]] auto str() const -> std::string const& { return str_; }
+  [[nodiscard]] auto x() const noexcept -> unsigned { return x_; }
+  [[nodiscard]] auto y() const noexcept -> unsigned { return y_; }
+
+  template<typename T>
+  void insert_moves(T inserter) const
+  {
+    Directions d{md5_directions(str_)};
+    if (x_ > 0 && (d & Directions::left) != Directions::none) {
+      *inserter++ = Node{str_ + 'L', x_ - 1, y_};
+    }
+    if (y_ > 0 && (d & Directions::up) != Directions::none) {
+      *inserter++ = Node{str_ + 'U', x_, y_ - 1};
+    }
+    if (x_ < 3 && (d & Directions::right) != Directions::none) {
+      *inserter++ = Node{str_ + 'R', x_ + 1, y_};
+    }
+    if (y_ < 3 && (d & Directions::down) != Directions::none) {
+      *inserter++ = Node{str_ + 'D', x_, y_ + 1};
+    }
+  }
+
+private:
+  Node(std::string s, unsigned x, unsigned y) : str_(std::move(s)), x_(x), y_(y) {}
+
+  std::string str_;
+  unsigned x_{0};
+  unsigned y_{0};
+};
+
+auto main() -> int
+{
+  std::string line;
+  if (!std::getline(std::cin, line)) {
+    std::cerr << "Failed to read line\n";
+    return 1;
+  }
+
+  Node initial_state{line};
+
+  std::set<Node> visited;
+  std::set<Node> to_visit;
+  to_visit.insert(initial_state);
+
+  std::size_t longest_path_len{0};
+  while (!to_visit.empty()) {
+    auto it{to_visit.begin()};
+    Node n{*it};
+    to_visit.erase(it);
+    visited.insert(n);
+    if (n.x() == 3 && n.y() == 3) {
+      auto path_len{n.str().size() - line.size()};
+      if (path_len > longest_path_len) {
+        longest_path_len = path_len;
+      }
+    }
+    else {
+      n.insert_moves(std::inserter(to_visit, to_visit.end()));
+    }
+  }
+
+  std::cout << "Longest path " << longest_path_len << '\n';
+  return 0;
+}