Add 2017 day 10 puzzles

2017/puzzle-10-01.cc

@@ -0,0 +1,55 @@
+#include <iostream>
+#include <numeric>
+#include <string>
+#include <vector>
+
+using UInt = unsigned long;
+using String = std::vector<UInt>;
+
+auto knot(String const& in, UInt current_position, UInt length) -> String
+{
+  String rot_left;
+  rot_left.reserve(in.size());
+  std::copy(in.begin() + current_position, in.end(), std::back_inserter(rot_left));
+  std::copy(in.begin(), in.begin() + current_position, std::back_inserter(rot_left));
+
+  std::reverse(rot_left.begin(), rot_left.begin() + length);
+
+  String rot_right;
+  std::copy(rot_left.end() - current_position, rot_left.end(), std::back_inserter(rot_right));
+  std::copy(rot_left.begin(), rot_left.end() - current_position, std::back_inserter(rot_right));
+  return rot_right;
+}
+
+auto main() -> int
+{
+  std::vector<UInt> string;
+  string.resize(256);
+  std::iota(string.begin(), string.end(), 0);
+
+  std::string line;
+  if (!std::getline(std::cin, line)) {
+    std::cerr << "Unable to read line.\n";
+    return 1;
+  }
+
+  std::size_t idx{0};
+  UInt current_pos{0};
+  UInt skip{0};
+  while (idx < line.size()) {
+    auto next{line.find(',', idx)};
+    if (next == std::string::npos) {
+      next = line.size();
+    }
+    auto len{next - idx};
+    auto length{std::stoul(line.substr(idx, len))};
+    string = knot(string, current_pos, length);
+    current_pos += length + skip;
+    current_pos %= string.size();
+    ++skip;
+    idx += len + 1;
+  }
+
+  std::cout << string[0] << " * " << string[1] << " = " << string[0] * string[1] << '\n';
+  return 0;
+}

2017/puzzle-10-02.cc

@@ -0,0 +1,73 @@
+#include <iomanip>
+#include <iostream>
+#include <numeric>
+#include <string>
+#include <vector>
+
+using UInt = unsigned char;
+using String = std::vector<UInt>;
+
+auto knot(String const& in, UInt current_position, UInt length) -> String
+{
+  String rot_left;
+  rot_left.reserve(in.size());
+  std::copy(in.begin() + current_position, in.end(), std::back_inserter(rot_left));
+  std::copy(in.begin(), in.begin() + current_position, std::back_inserter(rot_left));
+
+  std::reverse(rot_left.begin(), rot_left.begin() + length);
+
+  String rot_right;
+  std::copy(rot_left.end() - current_position, rot_left.end(), std::back_inserter(rot_right));
+  std::copy(rot_left.begin(), rot_left.end() - current_position, std::back_inserter(rot_right));
+  return rot_right;
+}
+
+auto main() -> int
+{
+  std::vector<UInt> string;
+  string.resize(256);
+  std::iota(string.begin(), string.end(), 0);
+
+  std::string line;
+  if (!std::getline(std::cin, line)) {
+    std::cerr << "Unable to read line.\n";
+    return 1;
+  }
+
+  /* Put the lengths into a vector.  */
+  std::vector<UInt> lengths;
+  lengths.reserve(line.size() + 5);
+  for (auto c : line) {
+    lengths.emplace_back(static_cast<UInt>(c));
+  }
+  lengths.emplace_back(17);
+  lengths.emplace_back(31);
+  lengths.emplace_back(73);
+  lengths.emplace_back(47);
+  lengths.emplace_back(23);
+
+  /* Run the hash */
+  UInt current_pos{0};
+  UInt skip{0};
+  for (unsigned i{0}; i < 64; ++i) {
+    for (auto length : lengths) {
+      string = knot(string, current_pos, length);
+      current_pos += length + skip;
+      ++skip;
+    }
+  }
+
+  /* Print the dense hash.  */
+  std::cout << "Dense hash: ";
+  unsigned hash{0};
+  for (unsigned i{0}; i < string.size(); ++i) {
+    hash ^= string[i];
+    if (i % 16 == 15) {
+      std::cout << std::hex << std::setw(2) << std::setfill('0') << hash;
+      hash = 0;
+    }
+  }
+  std::cout << '\n';
+
+  return 0;
+}