From d0f2fa688f76e9940b7d152e31ad5443a448ecd5 Mon Sep 17 00:00:00 2001
From: tristan <tristan@tristans.cloud>
Date: Wed, 4 Dec 2024 17:02:21 +0000
Subject: [PATCH] 2024 day 4 part 2

---
 2024/04/solution.nix      | 52 +++++++++++++++++++++++++
 2024/04/solution.test.nix | 82 ++++++++++++++++++++++++++++++++++++++-
 2 files changed, 133 insertions(+), 1 deletion(-)

diff --git a/2024/04/solution.nix b/2024/04/solution.nix
index 9aba538..4db9cea 100644
--- a/2024/04/solution.nix
+++ b/2024/04/solution.nix
@@ -69,4 +69,56 @@
     + findXMAS (rotated content)
     + findXMAS (diagonal (reversed content))
   ;
+
+  xmasMatcher = let
+    xmas = ''
+      M.S
+      .A.
+      M.S'';
+  in 
+    "${xmas}|${rotated xmas}|${reversed xmas}|${rotated (reversed xmas)}";
+
+  isX-MAS = s: s
+    |> builtins.match xmasMatcher
+    |> lib.isList
+  ;
+
+  break3s = s: let
+    len = builtins.length s - 2;
+  in
+    builtins.genList (i: lib.sublist i 3 s) len
+  ;
+
+  break3lines = s: s
+    |> lib.splitString "\n"
+    |> map lib.stringToCharacters
+    |> break3s
+  ;
+
+  log = t: lib.traceSeq t t;
+
+  break3x3s = l: l
+    |> map break3s
+    |> (groups:
+      let empty = builtins.elemAt groups 0 
+        |> builtins.length
+        |> genStrList [];
+      in builtins.foldl'
+      (lib.zipListsWith (a: b: a ++ ["\n"] ++ b))
+      empty groups)
+    |> map lib.concatStrings
+    |> map lib.trim
+  ;
+
+  break3x3 = s: s
+    |> break3lines
+    |> map break3x3s
+    |> builtins.concatLists
+  ;
+
+  part2result = content
+    |> break3x3
+    |> lib.count isX-MAS
+  ;
+
 }
diff --git a/2024/04/solution.test.nix b/2024/04/solution.test.nix
index 8e03679..22fc0f0 100644
--- a/2024/04/solution.test.nix
+++ b/2024/04/solution.test.nix
@@ -49,7 +49,7 @@ let
 in [
   (describe "part 1" [
     (it "gets content forward" {
-      actual = example.forward;
+      actual = example.content;
       expected = content;
     })
     (it "gets content rotated" {
@@ -77,4 +77,84 @@ in [
       expected = 18;
     })
   ])
+  (describe "part 2" [
+    (it "checks if string is X-MAS" {
+      actual = map example.isX-MAS [
+      ''
+        M.S
+        .A.
+        M.S''
+      ''
+        S.S
+        .A.
+        M.M''
+      ''
+        M.M
+        .A.
+        S.S''
+      ''
+        S.M
+        .A.
+        S.M''
+      ''
+        S.M
+        .A.
+        M.M''
+      ];
+      expected = [true true true true false];
+    })
+    (it "breaks list into 3s" {
+      actual = example.break3s [1 2 3 4 5];
+      expected = [[1 2 3] [2 3 4] [3 4 5]];
+    })
+    (it "breaks list into 3x3s" {
+      actual = example.break3x3s [
+        ["1" "2" "3" "4"]
+        ["5" "6" "7" "8"]
+        ["9" "A" "B" "C"]
+      ];
+      expected = [
+        ''
+        123
+        567
+        9AB''
+        ''
+        234
+        678
+        ABC''
+      ];
+    })
+    (it "breaks string into 3 lines" {
+      actual = example.break3lines ''
+        1234
+        5678
+        9ABC
+        DEFG'';
+      expected = [[
+        ["1" "2" "3" "4"]
+        ["5" "6" "7" "8"]
+        ["9" "A" "B" "C"]
+      ]
+      [
+        ["5" "6" "7" "8"]
+        ["9" "A" "B" "C"]
+        ["D" "E" "F" "G"]
+      ]];
+    })
+    (it "breaks string into 3x3 blocks" {
+      actual = example.break3x3 ''
+        1234
+        5678
+        9ABC
+        DEFG'';
+      expected = [
+        "123\n567\n9AB" "234\n678\nABC"
+        "567\n9AB\nDEF" "678\nABC\nEFG"
+      ];
+    })
+    (it "gets the result" {
+      actual = example.part2result;
+      expected = 9;
+    })
+  ])
 ]