day[08]: solution for Part 1 and Part 2

also added editorconfig and some fixes to scaffolding - it thought that
days were given in octal numbers. Codex, dammit!

.editorconfig

···
+# EditorConfig is awesome: https://EditorConfig.org
+
+# top-most EditorConfig file
+root = true
+
+# Unix-style newlines with a newline ending every file
+[*]
+end_of_line = lf
+insert_final_newline = true
+
+# 4 space indentation
+[*.cxx]
+indent_style = space
+indent_size = 4
+

Justfile

···
 
 # Run tests for a specific day. Defaults to today's day-of-month.
 test day=default_day: sync
-  day=$(printf '%02d' "{{day}}"); meson test -C build "day${day}"
+  day_raw="{{day}}"; day=$(printf '%02d' "$((10#$day_raw))"); meson test -C build "day${day}"
 
 # Run a day's solution on the "real" data set.
 run day=default_day: sync-release
-  day=$(printf '%02d' "{{day}}"); meson compile -C build-release "run-day${day}"
+  day_raw="{{day}}"; day=$(printf '%02d' "$((10#$day_raw))"); meson compile -C build-release "run-day${day}"
 
 # Clean the build folder. Useful... sometimes.
 clean:

data/08/input.txt

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data/08/test.txt

···
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src/08/solution.cxx

···
+#include <algorithm>
+#include <cmath>
+#include <fstream>
+#include <iterator>
+#include <map>
+#include <print>
+#include <ranges>
+#include <set>
+#include <vector>
+
+#include "common/getinputpath.h"
+#include "common/istest.h"
+
+const int STEPS = is_test() ? 10 : 1000;
+
+struct Box {
+    int x;
+    int y;
+    int z;
+
+    float euclidean(Box& other) {
+        return std::sqrt(std::pow((other.x - this->x), 2) +
+                         std::pow((other.y - this->y), 2) +
+                         std::pow((other.z - this->z), 2));
+    }
+
+    bool operator==(const Box other) const {
+        return this->x == other.x && this->y == other.y && this->z == other.z;
+    }
+
+    bool operator<(const Box other) const {
+        return this->x < other.x || (this->x == other.x && this->y < other.y) ||
+               (this->x == other.x && this->y == other.y && this->z < other.z);
+    }
+
+    std::string to_string() { return std::format("{} {} {}", x, y, z); }
+};
+
+struct Connection {
+    Box   a;
+    Box   b;
+    float distance;
+
+    bool operator==(const Connection& other) const {
+        return (other.a == this->a && other.b == this->b) ||
+               (other.a == this->b && other.b == this->a);
+    }
+
+    bool contains(Box box) { return this->a == box || this->b == box; }
+
+    bool connected(Connection connection) {
+        return this->contains(connection.a) || this->contains(connection.b);
+    }
+
+    bool operator<(const Connection other) const {
+        return this->distance < other.distance;
+    }
+};
+
+Connection make_connection(Box& one, Box& other) {
+    return Connection{.a = one, .b = other, .distance = one.euclidean(other)};
+}
+
+// standard DSU
+class DSU {
+    std::vector<int> size{};
+    std::vector<int> parent{};
+
+   public:
+    DSU(int n) {
+        parent.resize(n);
+        size.resize(n);
+
+        for (int i = 0; i < n; ++i) {
+            parent[i] = i;
+            size[i]   = 1;
+        }
+    }
+
+    int find(int i) {
+        return (parent[i] == i) ? i : (parent[i] = find(parent[i]));
+    }
+
+    void unite(int x, int y) {
+        int s1 = find(x);
+        int s2 = find(y);
+
+        if (s1 == s2) {
+            return;
+        }
+        if (size[s1] < size[s2]) {
+            parent[s1] = s2;
+            size[s2] += size[s1];
+        } else if (size[s1] > size[s2]) {
+            parent[s2] = s1;
+            size[s1] += size[s2];
+        } else {
+            parent[s2] = s1;
+            size[s1] += size[s2];
+        }
+    }
+
+    std::vector<int> sizes() { return size; }
+};
+
+int main() {
+    auto          path = get_input_path(DATA_FOLDER);
+    std::ifstream data_ifstream(path);
+    if (!data_ifstream.is_open()) {
+        std::println("Cannot open the file at {}", path.string());
+        return 1;
+    }
+
+    std::vector<Box> data{};
+    for (std::string t; std::getline(data_ifstream, t);) {
+        int x{};
+        int y{};
+        int z{};
+
+        auto first_comma_idx  = t.find_first_of(',');
+        auto x_str            = t.substr(0, first_comma_idx);
+        auto yz_str           = t.substr(first_comma_idx + 1);
+        auto second_comma_idx = yz_str.find_first_of(',');
+        auto y_str            = yz_str.substr(0, second_comma_idx);
+        auto z_str            = yz_str.substr(second_comma_idx + 1);
+
+        x = std::stoi(x_str);
+        y = std::stoi(y_str);
+        z = std::stoi(z_str);
+
+        data.push_back(Box{.x = x, .y = y, .z = z});
+    }
+
+    long long estimated_conns = data.size() * data.size() - data.size();
+    std::print("Generating connections... est. {}", estimated_conns);
+
+    // replacing this with an unordered set would make things faster
+    std::set<Connection> connections{};
+    for (auto box1 : data) {
+        for (auto box2 : data) {
+            if (box1 == box2) {
+                continue;
+            }
+
+            Connection conn = make_connection(box1, box2);
+            if (connections.contains(conn)) {  // connection already exists
+                continue;
+            }
+            connections.insert(conn);
+            std::print("\r");
+        }
+    }
+    std::println();
+
+    std::println("Sorting connections...");
+    std::vector<Connection> connections_vec =
+        connections | std::ranges::to<std::vector<Connection>>();
+    std::ranges::sort(connections_vec, [](Connection one, Connection other) {
+        return one.distance < other.distance;
+    });
+
+    std::println("Calculating three largest connected components...");
+    DSU dsu(data.size());
+
+    std::map<Box, size_t> data_idxs{};
+    for (auto [idx, box] : data | std::ranges::views::enumerate) {
+        data_idxs[box] = idx;
+    }
+
+    long long  counter = 0;
+    Connection last_connected;
+    long long  password_part_1;
+    for (auto conn : connections_vec) {
+        counter += 1;
+        if (dsu.find(data_idxs[conn.a]) != dsu.find(data_idxs[conn.b])) {
+            dsu.unite(data_idxs[conn.a], data_idxs[conn.b]);
+            last_connected = conn;
+        }
+        if (counter == STEPS) {
+            auto sizes = dsu.sizes();
+            std::ranges::sort(sizes);
+            std::ranges::reverse(sizes);
+
+            std::println("Three biggest: {}, {}, {}", sizes[0], sizes[1],
+                         sizes[2]);
+            int s1          = sizes[0];
+            int s2          = sizes[1];
+            int s3          = sizes[2];
+            password_part_1 = s1 * s2 * s3;
+        }
+    }
+
+    long long password_part_2 = last_connected.a.x * last_connected.b.x;
+
+    std::println();
+    std::println("Eureka! {} / {}", password_part_1, password_part_2);
+
+    return 0;
+}