knothash stuff

2017/10.cpp

@@ -0,0 +1,25 @@
+#include <cstdint>
+#include <string>
+#include <iostream>
+#include <vector>
+
+#include <doctest.h>
+
+#include <aocpp/Startup.hpp>
+#include <aocpp/Parsing.hpp>
+#include <knothash.hpp>
+
+auto main(int argc, char** argv) -> int {
+  std::string line;
+  std::getline(*aocpp::Startup(argc, argv), line);
+
+  std::vector<std::uint8_t> lengths1;
+  for (auto && x : aocpp::SplitOn(line, ",")) {
+    lengths1.push_back(std::stoul(x));
+  }
+
+  auto result = knothash::hash_ex<256>(1, lengths1.begin(), lengths1.end());
+  std::cout << "Part 1: " << long{result[0]} * long{result[1]} << std::endl;
+
+  std::cout << "Part 2: " << knothash::render(knothash::hash(line)) << std::endl;
+}

2017/14.cpp

@@ -0,0 +1,103 @@
+#include <array>
+#include <bit>
+#include <cstdint>
+#include <iostream>
+#include <optional>
+#include <string>
+#include <vector>
+
+#include <doctest.h>
+
+#include <aocpp/Startup.hpp>
+#include <aocpp/Parsing.hpp>
+#include <knothash.hpp>
+
+namespace {
+
+using Grid = std::vector<std::array<std::uint8_t, 16>>;
+
+auto MakeRows(std::string input) -> Grid {
+  Grid rows;
+  rows.reserve(128);
+
+  input += "-";
+  for (int i = 0; i < 128; i++) {
+    rows.emplace_back(knothash::hash(input + std::to_string(i)));
+  }
+
+  return rows;
+}
+
+auto CountBits(Grid const& grid) -> std::size_t {
+  std::size_t bits = 0;
+  for (auto const& row : grid) {
+    for (auto const x : row) {
+      bits += std::popcount(x);
+    }
+  }
+  return bits;
+}
+
+auto Connect(std::vector<std::uint16_t> & leaders, std::uint16_t who, std::uint16_t leader) {
+  auto who_ = leaders[who];
+  if (who_ == std::uint16_t(-1)) { return; } // there wasn't a node here, abort
+  for (;;) {
+    leaders[who] = leader;
+    if (who_ == who) { return; }
+    who = who_;
+    who_ = leaders[who];
+  }
+}
+
+auto CountComponents(Grid const& grid) -> std::uint16_t {
+
+  std::vector<std::uint16_t> leaders(128 * 128);
+
+  // Visit all pairs of neighbors linking them if both are set
+  for (std::uint16_t r = 0; r < 128; r++) {
+    bool prev = false;
+    for (std::uint16_t c = 0; c < 128; c++) {
+      std::uint16_t me = r*128+c;
+
+      // first time we've visited this node, if it's in the graph it's a leader!
+      if (grid[r][c/8] & (1<<(7-(c%8)))) {
+        leaders[me] = me;
+
+        // If previous cell in row is a node, link it to me immediately
+        // It will have just been set as its own group leader.
+        if (prev) { leaders[me-1] = me; }
+
+        // Connect up's leader _after_ updating left's leader in case they were connected
+        if (0 < r) { Connect(leaders, me - 128, me); }
+        prev = true;
+      } else {
+        prev = false;
+        leaders[me] = -1;
+      }
+    }
+  }
+
+  // count component leaders
+  std::uint16_t n = 0;
+  for (std::size_t i = 0; i < leaders.size(); i++) {
+    if (leaders[i] == i) { n++; }
+  }
+
+  return n;
+}
+
+} // namespace
+
+TEST_CASE("documented example") {
+  auto rows = MakeRows("flqrgnkx");
+  CHECK(CountBits(rows) == 8108);
+  CHECK(CountComponents(rows) == 1242);
+}
+
+auto main(int argc, char** argv) -> int {
+  std::string input;
+  std::getline(*aocpp::Startup(argc, argv), input);
+  auto rows = MakeRows(std::move(input));
+  std::cout << "Part 1: " << CountBits(rows) << std::endl;
+  std::cout << "Part 2: " << CountComponents(rows) << std::endl;
+}

2017/CMakeLists.txt

@@ -1,2 +1,8 @@
+add_executable(2017_10 10.cpp)
+target_link_libraries(2017_10 aocpp knothash)
+
+add_executable(2017_14 14.cpp)
+target_link_libraries(2017_14 aocpp knothash)
+
 add_executable(2017_18 18.cpp)
 target_link_libraries(2017_18 aocpp)