Add solution for 2021 day 15 part 1

2021/README.md

@@ -18,7 +18,7 @@
 | 12  |   ✓    |   ✓    | [Python]  |
 | 13  |   ✓    |   ✓    | [C++]     |
 | 14  |   ✓    |   ✓    | [Erlang]  |
-| 15  |        |        |           |
+| 15  |   ✓    |        | [D]       |
 | 16  |        |        |           |
 | 17  |        |        |           |
 | 18  |        |        |           |
@@ -50,3 +50,4 @@
 [python]: https://www.python.org
 [c++]: https://isocpp.org
 [erlang]: https://www.erlang.org
+[d]: https://dlang.org

2021/day-15/.gitignore

@@ -0,0 +1 @@
+*.o

2021/day-15/Justfile

@@ -0,0 +1,6 @@
+@part PART INPUT_FILE="inputs/puzzle.txt":
+    dmd -of=part_{{PART}} part_{{PART}}.d common.d
+    ./part_{{PART}} {{INPUT_FILE}}
+
+clean:
+    rm -f *.o part_one part_two

2021/day-15/common.d

@@ -0,0 +1,191 @@
+module common;
+
+import std.algorithm.iteration : filter, map;
+import std.algorithm.searching : minElement, canFind;
+import std.array : split;
+import std.container.array : Array;
+import std.conv : to;
+import std.stdio;
+import std.string : stripRight;
+import std.typecons : tuple, Tuple;
+
+private alias Buffer = Array!(Array!(uint));
+
+struct CaveMap
+{
+    private Buffer positions;
+
+    this(string path)
+    {
+        positions = parseFile(path);
+    }
+
+    private Array!(Array!uint) parseFile(string path)
+    {
+        auto file = File(path, "r");
+
+        auto buffer = Buffer();
+        string line;
+        while ((line = file.readln()) !is null)
+        {
+            auto line_buffer = Array!uint();
+
+            foreach (weight; split(stripRight(line), "").map!(to!uint))
+            {
+                line_buffer.insertBack(weight);
+            }
+
+            buffer.insertBack(line_buffer);
+        }
+
+        return buffer;
+
+    }
+}
+
+private alias NodeId = Tuple!(uint, uint);
+
+private struct Node
+{
+    private NodeId id;
+    private uint weight;
+
+    void toString(scope void delegate(const(char)[]) sink) const
+    {
+        sink("(");
+        sink(to!string(this.id[0]));
+        sink(",");
+        sink(to!string(this.id[1]));
+        sink(";");
+        sink(to!string(this.weight));
+        sink(")");
+    }
+}
+
+struct Cave
+{
+    private Array!Node[NodeId] nodes;
+    private NodeId start_node;
+    private NodeId end_node;
+
+    this(CaveMap cave_map)
+    {
+        auto node_id = NodeId(0, 0);
+        start_node = node_id;
+
+        uint y = 0;
+        foreach (row; cave_map.positions)
+        {
+            uint x = 0;
+            foreach (weight; row)
+            {
+                node_id = tuple(x, y);
+                nodes[node_id] = getNeighbors(x, y, cave_map.positions);
+
+                x++;
+            }
+
+            y++;
+        }
+
+        end_node = node_id;
+    }
+
+    uint lowestRisk()
+    {
+        auto safest_path = dijkstraSlow();
+        return safest_path[1][end_node];
+    }
+
+    private Tuple!(NodeId[NodeId], uint[NodeId]) dijkstraSlow()
+    {
+        bool[NodeId] unvisited;
+        uint[NodeId] distance;
+        NodeId[NodeId] previous;
+
+        foreach (node_id; nodes.byKey())
+        {
+            unvisited[node_id] = true;
+            distance[node_id] = uint.max;
+        }
+
+        distance[start_node] = 0;
+
+        unvisited.rehash;
+        distance.rehash;
+
+        while (unvisited.length != 0)
+        {
+            auto cur_node = unvisited.keys.minElement!(x => distance[x]);
+
+            if (cur_node == end_node)
+            {
+                break;
+            }
+
+            unvisited.remove(cur_node);
+
+            foreach (neighbor; nodes[cur_node])
+            {
+                if ((neighbor.id in unvisited) is null)
+                    continue;
+
+                auto total_distance = distance[cur_node] + neighbor.weight;
+
+                if (total_distance < distance[neighbor.id])
+                {
+                    distance[neighbor.id] = total_distance;
+                    previous[neighbor.id] = cur_node;
+                }
+            }
+        }
+
+        return tuple(previous, distance);
+    }
+
+    private immutable int[2][4] DIRECTIONS = [
+        [-1, 0], [1, 0],
+        [0, -1], [0, 1],
+    ];
+
+    private Array!Node getNeighbors(uint x, uint y, Buffer buf)
+    {
+        auto nodes = Array!Node();
+
+        foreach (dir; DIRECTIONS)
+        {
+            int dx = x + dir[0];
+            int dy = y + dir[1];
+
+            if (dx < 0 || dy < 0)
+                continue;
+            if (dx >= buf[0].length() || dy >= buf.length())
+                continue;
+
+            Node node = {id: tuple(dx, dy), buf[dy][dx]};
+
+            nodes.insertBack(node);
+        }
+
+        return nodes;
+    }
+
+    void toString(scope void delegate(const(char)[]) sink) const
+    {
+        foreach (id; this.nodes.byKey())
+        {
+            auto nodes = this.nodes[id];
+            sink("(");
+            sink(to!string(id[0]));
+            sink(",");
+            sink(to!string(id[1]));
+            sink(") { ");
+            foreach (node; nodes)
+            {
+                sink(to!string(node));
+                sink(" ");
+            }
+            sink("}\n");
+        }
+    }
+}

2021/day-15/inputs/puzzle.txt

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2021/day-15/inputs/sample.txt

@@ -0,0 +1,10 @@
+1163751742
+1381373672
+2136511328
+3694931569
+7463417111
+1319128137
+1359912421
+3125421639
+1293138521
+2311944581

2021/day-15/part_one.d

@@ -0,0 +1,12 @@
+import std.stdio;
+import common : CaveMap, Cave;
+
+void main(string[] args)
+{
+    auto immutable path = args[1];
+
+    auto cave_map = CaveMap(path);
+    auto graph = Cave(cave_map);
+
+    writeln(graph.lowestRisk());
+}

README.md

@@ -8,4 +8,4 @@
 -   [2018](2018/README.md) (0% completed)
 -   [2019](2019/README.md) (0% completed)
 -   [2020](2020/README.md) (20% completed)
--   [2021](2021/README.md) (56% completed)
+-   [2021](2021/README.md) (58% completed)