2024/04

encse · Dec 4, 2024 · b316bdc · b316bdc
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diff --git a/2024/Day04/README.md b/2024/Day04/README.md
@@ -0,0 +1,8 @@
+## --- Day 4: Ceres Search ---
+"Looks like the Chief's not here. Next!" One of The Historians pulls out a device and pushes the only button on it. After a brief flash, you recognize the interior of the [Ceres monitoring station](/2019/day/10)!
+
+As the search for the Chief continues, a small Elf who lives on the station tugs on your shirt; she'd like to know if you could help her with her <em>word search</em> (your puzzle input). She only has to find one word: <code>XMAS</code>.
+
+This word search allows words to be horizontal, vertical, diagonal, written backwards, or even overlapping other words. It's a little unusual, though, as you don't merely need to find one instance of <code>XMAS</code> - you need to find <em>all of them</em>. Here are a few ways <code>XMAS</code> might appear, where irrelevant characters have been replaced with <code>.</code>:
+
+Read the [full puzzle](https://adventofcode.com/2024/day/4).
diff --git a/2024/Day04/Solution.cs b/2024/Day04/Solution.cs
@@ -0,0 +1,61 @@
+namespace AdventOfCode.Y2024.Day04;
+
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Numerics;
+using System.Linq;
+
+using Map = System.Collections.Immutable.ImmutableDictionary<System.Numerics.Complex, char>;
+
+[ProblemName("Ceres Search")]
+class Solution : Solver {
+
+    Complex Up = -Complex.ImaginaryOne;
+    Complex Down = Complex.ImaginaryOne;
+    Complex Left = -1;
+    Complex Right = 1;
+
+    public object PartOne(string input) {
+        var mat = GetMap(input);
+        return (
+            from pt in mat.Keys
+            from dir in  new[] { Right, Right + Down, Down + Left, Down}
+            where Matches(mat, pt, dir, "XMAS")
+            select 1
+        ).Count();
+    }
+
+    public object PartTwo(string input) {
+        var mat = GetMap(input);
+        return (
+            from pt in mat.Keys
+            where 
+                Matches(mat, pt + Up + Left, Down + Right, "MAS") && 
+                Matches(mat, pt + Down + Left, Up + Right, "MAS")
+            select 1
+        ).Count();
+    }
+
+    // check if the pattern (or its reverse) can be read in the given direction 
+    // starting from pt
+    bool Matches(Map map, Complex pt, Complex dir, string pattern) {
+        var chars = Enumerable.Range(0, pattern.Length)
+            .Select(i => map.GetValueOrDefault(pt + i * dir))
+            .ToArray();
+        return
+            Enumerable.SequenceEqual(chars, pattern) ||
+            Enumerable.SequenceEqual(chars, pattern.Reverse());
+    }
+
+    // store the points in a dictionary so that we can iterate over them and 
+    // to easily deal with points outside the area using GetValueOrDefault
+    Map GetMap(string input) {
+        var map = input.Split("\n");
+        return (
+            from y in Enumerable.Range(0, map.Length)
+            from x in Enumerable.Range(0, map[0].Length)
+            select new KeyValuePair<Complex, char>(Complex.ImaginaryOne * y + x, map[y][x])
+        ).ToImmutableDictionary();
+    }
+}
diff --git a/2024/Day04/input.in b/2024/Day04/input.in
diff --git a/2024/Day04/input.refout b/2024/Day04/input.refout
@@ -0,0 +1,2 @@
+2414
+1871
diff --git a/2024/SplashScreen.cs b/2024/SplashScreen.cs
@@ -8,8 +8,8 @@ public void Show() {
 
         var color = Console.ForegroundColor;
         Write(0xcc00, false, "           ▄█▄ ▄▄█ ▄ ▄ ▄▄▄ ▄▄ ▄█▄  ▄▄▄ ▄█  ▄▄ ▄▄▄ ▄▄█ ▄▄▄\n           █▄█ █ █ █ █ █▄█ █ █ █   █ █ █▄ ");
-            Write(0xcc00, false, " █  █ █ █ █ █▄█\n           █ █ █▄█ ▀▄▀ █▄▄ █ █ █▄  █▄█ █   █▄ █▄█ █▄█ █▄▄  {'year': 2024}\n          ");
-            Write(0xcc00, false, "  \n                  ");
+            Write(0xcc00, false, " █  █ █ █ █ █▄█\n           █ █ █▄█ ▀▄▀ █▄▄ █ █ █▄  █▄█ █   █▄ █▄█ █▄█ █▄▄  $year = 2024\n            ");
+            Write(0xcc00, false, "\n                  ");
             Write(0xcccccc, false, ".--'");
             Write(0xe3b585, false, "~ ~ ~");
             Write(0xcccccc, false, "|        .-' ");
@@ -47,21 +47,40 @@ public void Show() {
             Write(0x886655, false, "__------");
             Write(0xcccccc, false, "|   3 ");
             Write(0xffff66, false, "**\n           ");
-            Write(0x333333, false, "|               |        |                      |  ");
-            Write(0x666666, false, " 4\n                                                               5\n                                ");
-            Write(0x666666, false, "                               6\n                                                               7\n  ");
-            Write(0x666666, false, "                                                             8\n                                     ");
-            Write(0x666666, false, "                          9\n                                                              10\n       ");
-            Write(0x666666, false, "                                                       11\n                                          ");
-            Write(0x666666, false, "                    12\n                                                              13\n            ");
-            Write(0x666666, false, "                                                  14\n                                               ");
-            Write(0x666666, false, "               15\n                                                              16\n                 ");
-            Write(0x666666, false, "                                             17\n                                                    ");
-            Write(0x666666, false, "          18\n                                                              19\n                      ");
-            Write(0x666666, false, "                                        20\n                                                         ");
-            Write(0x666666, false, "     21\n                                                              22\n                           ");
-            Write(0x666666, false, "                                   23\n                                                              ");
-            Write(0x666666, false, "24\n                                                              25\n           \n");
+            Write(0xcccccc, false, "|");
+            Write(0x1461f, false, "@");
+            Write(0x5eabb4, false, "..");
+            Write(0x7fbd39, false, "@");
+            Write(0xe3b585, false, "'. ~ ");
+            Write(0xcc00, false, "\" ' ");
+            Write(0xe3b585, false, "~ ");
+            Write(0xcccccc, false, "|        |");
+            Write(0x9900, false, ">");
+            Write(0x66ff, true, "O");
+            Write(0x9900, false, ">");
+            Write(0xff9900, true, "o");
+            Write(0x9900, false, "<");
+            Write(0xff0000, true, "@");
+            Write(0x9900, false, "< ");
+            Write(0x886655, false, "\\____       ");
+            Write(0xcc00, false, ".'");
+            Write(0xcccccc, false, "|   4 ");
+            Write(0xffff66, false, "**\n           ");
+            Write(0x333333, false, "|               |        |          ..          |  ");
+            Write(0x666666, false, " 5\n                                                               6\n                                ");
+            Write(0x666666, false, "                               7\n                                                               8\n  ");
+            Write(0x666666, false, "                                                             9\n                                     ");
+            Write(0x666666, false, "                         10\n                                                              11\n       ");
+            Write(0x666666, false, "                                                       12\n                                          ");
+            Write(0x666666, false, "                    13\n                                                              14\n            ");
+            Write(0x666666, false, "                                                  15\n                                               ");
+            Write(0x666666, false, "               16\n                                                              17\n                 ");
+            Write(0x666666, false, "                                             18\n                                                    ");
+            Write(0x666666, false, "          19\n                                                              20\n                      ");
+            Write(0x666666, false, "                                        21\n                                                         ");
+            Write(0x666666, false, "     22\n                                                              23\n                           ");
+            Write(0x666666, false, "                                   24\n                                                              ");
+            Write(0x666666, false, "25\n           \n");
 
         Console.ForegroundColor = color;
         Console.WriteLine();

diff --git a/2024/calendar.svg b/2024/calendar.svg