8

CMakeLists.txt

@@ -38,6 +38,9 @@ target_link_libraries(day06 aocpp)
 add_executable(day07 day07.cpp)
 target_link_libraries(day07 aocpp intcode)
 
+add_executable(day08 day08.cpp)
+target_link_libraries(day08 aocpp)
+
 add_executable(day09 day09.cpp)
 target_link_libraries(day09 aocpp intcode)
 

day08.cpp

@@ -0,0 +1,74 @@
+#include <algorithm>
+#include <cstdint>
+#include <array>
+#include <iostream>
+#include <iterator>
+#include <vector>
+
+#include <aocpp/Startup.hpp>
+
+namespace {
+
+using Layer = std::array<char, 150>;
+
+auto SplitLayers(std::istream & in) {
+  std::string line;
+  std::getline(in, line);
+
+  std::vector<Layer> layers;
+
+  auto it = line.begin();
+  auto layer_n = line.size() / 150;
+  for (std::size_t layer = 0; layer < layer_n; layer++) {
+    layers.push_back({});
+    for (std::size_t y = 0; y < 150; y++) {
+      layers.back()[y] = *it++;
+    }
+  }
+  return layers;
+}
+
+auto Part1(std::vector<Layer> const& layers) {
+  std::size_t part1 = 0;
+  std::size_t seen = std::numeric_limits<std::size_t>::max();
+  for (auto & layer : layers) {
+    auto zeros = std::count(layer.begin(), layer.end(), '0');
+    if (zeros < seen) {
+      seen = zeros;
+      part1
+        = std::count(layer.begin(), layer.end(), '1')
+        * std::count(layer.begin(), layer.end(), '2');
+    }
+  }
+  return part1;
+}
+
+auto Flatten(std::vector<Layer> const& layers) {
+  Layer merged {};
+  for (std::size_t i = 0; i < 150; i++) {
+    for (auto & layer : layers) {
+      if ('2' != layer[i]) {
+        merged[i] = layer[i];
+        break;
+      }
+    }
+  }
+  return merged;
+}
+
+auto Draw(Layer picture) {
+  for (std::size_t y = 0; y < 6; y++) {
+    for (std::size_t x = 0; x < 25; x++) {
+      std::cout << ('1' == picture[y*25+x] ? "▓" : "░");
+    }
+    std::cout << std::endl;
+  }
+}
+
+} // namespace
+
+auto main(int argc, char** argv) -> int {
+  auto layers = SplitLayers(aocpp::Startup(argc, argv));
+  std::cout << "Part 1: " << Part1(layers) << std::endl;
+  Draw(Flatten(layers));
+}