2025/02

Author: encse

2025/Day02/README.md

@@ -0,0 +1,6 @@
+## --- Day 2: Gift Shop ---
+You get inside and take the elevator to its only other stop: the gift shop. "Thank you for visiting the North Pole!" gleefully exclaims a nearby sign. You aren't sure who is even allowed to visit the North Pole, but you know you can access the lobby through here, and from there you can access the rest of the North Pole base.
+
+As you make your way through the surprisingly extensive selection, one of the clerks recognizes you and asks for your help.
+
+_Visit the website for the full story and [full puzzle](https://adventofcode.com/2025/day/2) description._

2025/Day02/Solution.cs

@@ -0,0 +1,45 @@
+namespace AdventOfCode.Y2025.Day02;
+
+using System;
+using System.Linq;
+using System.Collections.Generic;
+
+[ProblemName("Gift Shop")]
+class Solution : Solver {
+
+    public object PartOne(string input) => Solve(input, st => 2);
+
+    public object PartTwo(string input) => Solve(input, st => st.Length);
+
+    long Solve(string input, Func<string, int> maxRepetition) => (
+        from id in GetIds(input)
+        let st = id.ToString()
+        where Enumerable.Range(2, maxRepetition(st)-1).Any(k => Periodic(st, k))
+        select id
+    ).Sum();
+
+    public IEnumerable<long> GetIds(string input) {
+        foreach (var range in input.Split(",")) {
+            var parts = range.Split("-").Select(long.Parse).ToArray();
+            for (var i = parts[0]; i <= parts[1]; i++) {
+                yield return i;
+            }
+        }
+    }
+
+    // Returns true if the string consists of the same substring repeated repetitionCount times.
+    // Example: repetitionCount == 3 returns true for "abcabcabc".
+    bool Periodic(string st, int repetitionCount) {
+        if (st.Length % repetitionCount != 0) {
+            return false;
+        }
+
+        int period = st.Length / repetitionCount;
+        for (int i = period; i < st.Length; i += period) {
+            if (st[..period] != st[i..(i + period)]) {
+                return false;
+            }
+        }
+        return true;
+    }
+}

2025/Day02/input.in

@@ -0,0 +1,2 @@
+32976912643
+54446379122

2025/Day02/input.refout

@@ -8,24 +8,49 @@ public void Show() {
 
         var color = Console.ForegroundColor;
         Write(0xcc00, false, "           ▄█▄ ▄▄█ ▄ ▄ ▄▄▄ ▄▄ ▄█▄  ▄▄▄ ▄█  ▄▄ ▄▄▄ ▄▄█ ▄▄▄\n           █▄█ █ █ █ █ █▄█ █ █ █   █ █ █▄ ");
-            Write(0xcc00, false, " █  █ █ █ █ █▄█\n           █ █ █▄█ ▀▄▀ █▄▄ █ █ █▄  █▄█ █   █▄ █▄█ █▄█ █▄▄  /* 2025 */\n            \n ");
-            Write(0xcc00, false, "            ");
-            Write(0xffffff, false, "'.'.   ____ '     ... ");
+            Write(0xcc00, false, " █  █ █ █ █ █▄█\n           █ █ █▄█ ▀▄▀ █▄▄ █ █ █▄  █▄█ █   █▄ █▄█ █▄█ █▄▄  sub y{2025}\n            \n");
+            Write(0xcc00, false, "               ");
+            Write(0xffffff, false, "'    ____ '   .     ");
             Write(0xffff66, true, "*    ");
-            Write(0xffffff, false, "'  . .'  .. ");
+            Write(0xffffff, false, "'. .' .  '. ");
             Write(0xff9900, false, "<");
             Write(0xffffff, false, "o  ' .        \n           ________/");
             Write(0x999999, false, "O___");
             Write(0xffffff, false, "\\__________");
             Write(0xff0000, false, "|");
             Write(0xffffff, false, "_________________O______  ");
             Write(0xcccccc, false, " 1 ");
-            Write(0xffff66, false, "**\n           ");
-            Write(0x333333, false, "   _______||_________                                   \n              | _@__ || _o_    |           ");
-            Write(0x333333, false, "                   ");
-            Write(0x666666, false, " 2\n           ");
-            Write(0x333333, false, "   |_&_%__||_oo__^=_[                                   \n                                           ");
-            Write(0x333333, false, "                   ");
+            Write(0xffff66, false, "**\n              ");
+            Write(0x999999, false, "_______");
+            Write(0xaabbcc, false, "||");
+            Write(0x999999, false, "_________                                   \n              | ");
+            Write(0x9b715b, false, "_");
+            Write(0xbb66ff, false, "@");
+            Write(0x9b715b, false, "__ ");
+            Write(0xaabbcc, false, "|| ");
+            Write(0x9b715b, false, "_");
+            Write(0x66ff, false, "o");
+            Write(0x9b715b, false, "_  ");
+            Write(0xff0000, false, "'.");
+            Write(0x999999, false, "|");
+            Write(0x666666, false, "_ _________________________   ");
+            Write(0xcccccc, false, " 2 ");
+            Write(0xffff66, false, "**\n              ");
+            Write(0x999999, false, "|_");
+            Write(0xff0000, false, "&");
+            Write(0x999999, false, "_");
+            Write(0xffff66, false, "%");
+            Write(0x999999, false, "__");
+            Write(0xaabbcc, false, "||");
+            Write(0x999999, false, "_");
+            Write(0x66ff, false, "o");
+            Write(0xff9900, false, "o");
+            Write(0x999999, false, "__");
+            Write(0xaabbcc, false, "^");
+            Write(0x9b715b, false, "=");
+            Write(0x999999, false, "_");
+            Write(0x9b715b, false, "[");
+            Write(0x333333, false, " \\|     _    .. .. ..     |        \n                                \\_]__--|_|___[]_[]_[]__//_|   ");
             Write(0x666666, false, " 3\n                                                                   \n                             ");
             Write(0x666666, false, "                                  4\n                                                                ");
             Write(0x666666, false, "   \n                                                               5\n                               ");