Day 11

src/cpp/11_ylks.cpp

@@ -0,0 +1,93 @@
+#include "io_utils.hpp"
+
+#include <algorithm>
+#include <vector>
+#include <string>
+#include <numeric>
+#include <set>
+
+using Map = std::vector<std::string>;
+using Coord = std::pair<int, int>;
+using ExpansionSet = std::pair<std::set<size_t>, std::set<size_t>>;
+
+ExpansionSet convertMap(std::vector<std::string> & lines) {
+    ExpansionSet space;
+    for (size_t idx = 0; idx < lines.size(); idx++) {
+        if (std::all_of(lines.at(idx).begin(), lines.at(idx).end(), [](const auto c){return c == '.';})) {
+            space.first.insert(idx);
+        }
+    }
+
+    for (size_t idx = 0; idx < lines.front().size(); ++idx) {
+        bool all_dots = true;
+        for (size_t row_idx = 0; row_idx < lines.size(); ++row_idx) {
+            all_dots &= lines.at(row_idx).at(idx) == '.';
+        }
+
+        if (all_dots) {
+            space.second.insert(idx);
+        }
+    }
+
+    return space;
+}
+
+std::vector<Coord> getGalaxies(const Map & map) {
+    std::vector<Coord> ret;
+    for (int row_idx = 0; row_idx < map.size(); row_idx++) {
+        for (int col_idx = 0; col_idx < map.front().size(); col_idx++) {
+            if (map[row_idx][col_idx] == '#') {
+                ret.emplace_back(row_idx, col_idx);
+            }
+        }
+    }
+    return ret;
+}
+
+int manhattanDist(const Coord & a, const Coord & b) {
+    return std::abs(a.first - b.first) + std::abs(a.second - b.second);
+}
+
+int getNumEmptySpaces(int min_val, int max_val, const std::set<size_t> & space) {
+    auto lower = space.lower_bound(min_val);
+    auto upper = space.upper_bound(max_val);
+    return std::distance(lower, upper);
+}
+
+long spaceDistance(const Coord& a, const Coord & b, const ExpansionSet & space, const int expansion_factor) {
+    int min_x = std::min(a.first, b.first);
+    int max_x = std::max(a.first, b.first);
+    int min_y = std::min(a.second, b.second);
+    int max_y = std::max(a.second, b.second);
+
+    long extra_values = getNumEmptySpaces(min_x, max_x, space.first) * expansion_factor
+        + getNumEmptySpaces(min_y, max_y, space.second) * expansion_factor;
+    return  extra_values + manhattanDist(a, b);
+}
+
+long sumOfShortestPairWise(const std::vector<Coord> & coords, const ExpansionSet & space, const int expansion_factor) {
+    long sum = 0;
+    for (size_t idx = 0; idx < coords.size(); ++idx) {
+        for (size_t idx2 = idx + 1; idx2 < coords.size(); idx2++) {
+            sum += spaceDistance(coords.at(idx), coords.at(idx2), space, expansion_factor);
+        }
+    }
+    return sum;
+}
+
+int main(int argc, char** argv) {
+    if (argc < 2) {
+        std::cout << "No input given" << std::endl;
+        return 1;
+    }
+    std::string filename(argv[1]);
+    auto lines = io_utils::parseInputFile(filename);
+
+    const auto space = convertMap(lines);
+    auto g = getGalaxies(lines);
+
+    std::cout << sumOfShortestPairWise(g, space, 1) << std::endl;
+    std::cout << sumOfShortestPairWise(g, space, 1000000 - 1) << std::endl;
+
+    return 0;
+}

src/cpp/BUILD

@@ -102,3 +102,11 @@ cc_binary(
         "//src/cpp/shared_libs/io_utils:io_utils"
     ]
 )
+
+cc_binary(
+    name = "11_ylks",
+    srcs = ["11_ylks.cpp"],
+    deps = [
+        "//src/cpp/shared_libs/io_utils:io_utils"
+    ]
+)