Day 12

Author: bt

CMakeLists.txt

@@ -20,6 +20,7 @@ add_challenge(day8)
 add_challenge(day9)
 add_challenge(day10)
 add_challenge(day11)
+add_challenge(day12)
 
 add_custom_command(TARGET day1
     COMMAND ${CMAKE_COMMAND} -E create_symlink "${CMAKE_CURRENT_SOURCE_DIR}/data" "./data"

src/day12.cpp

@@ -0,0 +1,174 @@
+#include "common_headers.hpp"
+#include <array>
+#include <set>
+#include <stack>
+
+constexpr std::array<int,5> offsets{0, 1, 0, -1, 0};
+
+using CoordinateMap = std::set<std::pair<int, int>>;
+
+[[nodiscard]] size_t calculatePerimeter(const std::vector<std::string>& map, int row, int col) {
+    size_t perimeter{};
+    for(int i = 0; i < 4; ++i) {
+        const int newRow{row + offsets[i]};
+        const int newCol{col + offsets[i + 1]};
+        if(newRow < 0 || newCol < 0 || newRow >= map.size() || newCol >= map[0].size()) {
+            ++perimeter;
+        }
+        else {
+            perimeter += map[row][col] != map[newRow][newCol];
+        }
+    }
+    return perimeter;
+}
+
+[[nodiscard]] size_t calculateCorner(const std::vector<std::string>& map, int row, int col) {
+    size_t counter{};
+    const char plot{map[row][col]};
+    // top left outer
+    if((row - 1 < 0 || plot != map[row - 1][col]) && (col - 1 < 0 || map[row][col - 1] != plot)) {
+        ++counter;
+    }
+    // top right outer
+    if((row - 1 < 0 || plot != map[row - 1][col]) && (col + 1 >= map[0].size() || map[row][col + 1] != plot)) {
+        ++counter;
+    }
+    // bottom left
+    if((row + 1 >= map.size() || map[row + 1][col] != plot) && (col - 1 < 0 || map[row][col - 1] != plot)) {
+        ++counter;
+    }
+    // bottom right
+    if((row + 1 >= map.size() || map[row + 1][col] != plot) && (col + 1 >= map[0].size() || map[row][col + 1] != plot)) {
+        ++counter;
+    }
+
+    // top left inner
+    if(row - 1 >= 0 && map[row - 1][col] == plot && col - 1 >= 0 && map[row][col - 1] == plot && map[row - 1][col - 1] != plot) {
+        ++counter;
+    }
+
+    // top right inner
+    if(row - 1 >= 0 && map[row - 1][col] == plot && col + 1 < map[0].size() && map[row][col + 1] == plot && map[row - 1][col + 1] != plot) {
+        ++counter;
+    }
+
+    // bottom left inner
+    if(row + 1 < map.size() && map[row + 1][col] == plot && col - 1 >= 0 && map[row][col - 1] == plot && map[row + 1][col - 1] != plot) {
+        ++counter;
+    }
+    // bottom right inner
+    if(row + 1 < map.size() && map[row + 1][col] == plot && col + 1 < map[0].size() && map[row][col + 1] == plot && map[row + 1][col + 1] != plot) {
+        ++counter;
+    }
+
+    return counter;
+}
+
+
+template<typename Handler>
+void traverse(const std::vector<std::string>& map, int row, int col, CoordinateMap& visited, Handler& handler) {
+    
+    const char plot{map[row][col]};
+
+    std::stack<std::pair<int, int>> dfs;
+    dfs.emplace(row, col);
+
+    while(!dfs.empty()) {
+        const auto [r, c] = dfs.top();
+        dfs.pop();
+        if(visited.emplace(std::pair{r, c}).second == false) continue;
+
+        handler(map, r, c);
+
+        for(int i = 0; i < 4; ++i) {
+            const int newRow{r + offsets[i]};
+            const int newCol{c + offsets[i + 1]};
+            if(newRow < 0 || newCol < 0 || newRow >= map.size() || newCol >= map[0].size()) {
+                continue;
+            }
+            else if(plot == map[newRow][newCol]) {
+                dfs.emplace(newRow, newCol);
+            }
+        }
+    }
+}
+
+[[nodiscard]] size_t solveFirstPart(const std::vector<std::string>& map) {
+    size_t totalPrice{};
+    CoordinateMap visited;
+    
+
+    for(int row = 0; row < map.size(); ++row) {
+        for(int col = 0; col < map[0].size(); ++col) {
+            if(visited.count(std::pair(row, col))) continue;
+
+            size_t area{};
+            size_t perimeter{};
+            auto calculator = [&](const std::vector<std::string>& map, int row, int col) mutable {
+                ++area;
+                perimeter += calculatePerimeter(map, row, col);
+            };
+
+            traverse(map, row, col, visited, calculator);
+            totalPrice += area * perimeter;
+        }
+    }
+    return totalPrice;
+}
+
+[[nodiscard]] size_t solveSecondPart(const std::vector<std::string>& map) {
+    size_t totalPrice{};
+    CoordinateMap visited;
+
+    for(int row = 0; row < map.size(); ++row) {
+        for(int col = 0; col < map[0].size(); ++col) {
+            if(visited.count(std::pair(row, col))) continue;
+
+            size_t area{};
+            size_t perimeter{};
+            auto calculator = [&](const std::vector<std::string>& map, int row, int col) mutable {
+                ++area;
+                perimeter += calculateCorner(map, row, col);
+            };
+            traverse(map, row, col, visited, calculator);
+            totalPrice += area * perimeter;
+        }
+    }
+
+    return totalPrice;
+}
+
+
+void printHelp()
+{
+    std::cerr << "\nUsage:\n"
+    << "The program requires 2 args: (part1, part2) and the path to the file."
+    << "\nFor example, ./day7 part1 data/day7.txt";
+}
+
+int main(int argc, char* argv[])
+{
+    if(argc != 3) {
+        printHelp();
+        return 1;
+    }
+
+    std::string_view task{argv[1]};
+    if(task != "part1" && task != "part2") {
+        std::cerr << "\nfirst arg can be either `part1` or `part2`\n";
+        printHelp();
+        return 1;
+    }
+    
+    std::vector<std::string> inputVec;
+    readInput(argv[2], std::back_inserter(inputVec));
+
+    if(task == "part1") {
+        std::cout << solveFirstPart(inputVec);
+    }
+    else {
+        std::cout << solveSecondPart(inputVec);
+    }
+
+    return 0;
+}