From d9abf795bbd4ba221993a8115308de22bd2ae155 Mon Sep 17 00:00:00 2001
From: Tyler Beckman <ty@myriation.xyz>
Date: Fri, 13 Dec 2024 01:03:44 -0700
Subject: [PATCH] Day 13 but in nix this time

---
 day13/part1.nix | 76 ++++++++++++++++++++++++++++++++++++++++++++
 day13/part2.nix | 83 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 159 insertions(+)
 create mode 100644 day13/part1.nix
 create mode 100644 day13/part2.nix

diff --git a/day13/part1.nix b/day13/part1.nix
new file mode 100644
index 0000000..26ee766
--- /dev/null
+++ b/day13/part1.nix
@@ -0,0 +1,76 @@
+let
+    # Import nixpkgs lib and input file
+    inherit ((builtins.getFlake (builtins.toString ./..)).inputs.nixpkgs) lib;
+    input = builtins.readFile (builtins.toString ./input.txt);
+
+    # Define functions
+    matElem = row: col: mat: builtins.elemAt (builtins.elemAt mat row) col;
+    matDet = m: ((matElem 0 0 m) * (matElem 1 1 m)) - ((matElem 0 1 m) * (matElem 1 0 m));
+
+    # Parse input
+    split = builtins.map
+        (s:
+            let 
+                split = lib.strings.splitString "\n" s;
+            in  { a = builtins.elemAt split 0; b = builtins.elemAt split 1; prize = builtins.elemAt split 2; }
+        )
+        (lib.strings.splitString "\n\n" input);
+    extracted = builtins.map
+        ({ a, b, prize }: {
+            a = lib.strings.splitString ", Y+" (builtins.substring 12 (-1) a);
+            b = lib.strings.splitString ", Y+" (builtins.substring 12 (-1) b);
+            prize = lib.strings.splitString ", Y=" (builtins.substring 9 (-1) prize);
+        }) split;
+    numbered = builtins.map
+        ({ a, b, prize }: {
+            a = { x = lib.strings.toInt (builtins.elemAt a 0); y = lib.strings.toInt (builtins.elemAt a 1); };
+            b = { x = lib.strings.toInt (builtins.elemAt b 0); y = lib.strings.toInt (builtins.elemAt b 1); };
+            prize = { x = lib.strings.toInt (builtins.elemAt prize 0); y = lib.strings.toInt (builtins.elemAt prize 1); };
+        }) extracted;
+    
+    # Solve system of equations
+    mathified = builtins.map
+        ({ a, b, prize }: {
+            # First equation
+            a1 = a.x;
+            b1 = b.x;
+            c1 = prize.x;
+            # Second equation
+            a2 = a.y;
+            b2 = b.y;
+            c2 = prize.y;
+        }) numbered;
+    determinants = builtins.map
+        ({ a1, b1, c1, a2, b2, c2 }: {
+            numerators = {
+                a = matDet [
+                    [ c1 b1 ]
+                    [ c2 b2 ]
+                ];
+                b = matDet [
+                    [ a1 c1 ]
+                    [ a2 c2 ]
+                ];
+            };
+            denominator = matDet [
+                [ a1 b1 ]
+                [ a2 b2 ]
+            ];
+        }) mathified;
+    tokens = (
+        lib.lists.foldr
+            ({ numerators, denominator }: accumulated-tokens:
+                accumulated-tokens + (
+                    if (
+                        (lib.trivial.mod numerators.a denominator) != 0
+                        || (lib.trivial.mod numerators.b denominator) != 0
+                    )
+                    then 0
+                    else (numerators.a / denominator) * 3 + (numerators.b / denominator)
+                )
+            )
+            0
+    ) determinants;
+
+    output = tokens;
+in output
\ No newline at end of file
diff --git a/day13/part2.nix b/day13/part2.nix
new file mode 100644
index 0000000..c0a00ef
--- /dev/null
+++ b/day13/part2.nix
@@ -0,0 +1,83 @@
+let
+    # Import nixpkgs lib and input file
+    inherit ((builtins.getFlake (builtins.toString ./..)).inputs.nixpkgs) lib;
+    input = builtins.readFile (builtins.toString ./input.txt);
+
+    # Define functions
+    matElem = row: col: mat: builtins.elemAt (builtins.elemAt mat row) col;
+    matDet = m: ((matElem 0 0 m) * (matElem 1 1 m)) - ((matElem 0 1 m) * (matElem 1 0 m));
+
+    # Parse input
+    split = builtins.map
+        (s:
+            let 
+                split = lib.strings.splitString "\n" s;
+            in  { a = builtins.elemAt split 0; b = builtins.elemAt split 1; prize = builtins.elemAt split 2; }
+        )
+        (lib.strings.splitString "\n\n" input);
+    extracted = builtins.map
+        ({ a, b, prize }: {
+            a = lib.strings.splitString ", Y+" (builtins.substring 12 (-1) a);
+            b = lib.strings.splitString ", Y+" (builtins.substring 12 (-1) b);
+            prize = lib.strings.splitString ", Y=" (builtins.substring 9 (-1) prize);
+        }) split;
+    numbered = builtins.map
+        ({ a, b, prize }: {
+            a = { x = lib.strings.toInt (builtins.elemAt a 0); y = lib.strings.toInt (builtins.elemAt a 1); };
+            b = { x = lib.strings.toInt (builtins.elemAt b 0); y = lib.strings.toInt (builtins.elemAt b 1); };
+            prize = { x = lib.strings.toInt (builtins.elemAt prize 0); y = lib.strings.toInt (builtins.elemAt prize 1); };
+        }) extracted;
+
+    # PART 2 DIFFERENCE: Add 10000000000000 to prize x & y
+    added = builtins.map
+        ({ a, b, prize }: {
+            inherit a b;
+            prize = { x = prize.x + 10000000000000; y = prize.y + 10000000000000; };
+        }) numbered;
+    
+    # Solve system of equations
+    mathified = builtins.map
+        ({ a, b, prize }: {
+            # First equation
+            a1 = a.x;
+            b1 = b.x;
+            c1 = prize.x;
+            # Second equation
+            a2 = a.y;
+            b2 = b.y;
+            c2 = prize.y;
+        }) added;
+    determinants = builtins.map
+        ({ a1, b1, c1, a2, b2, c2 }: {
+            numerators = {
+                a = matDet [
+                    [ c1 b1 ]
+                    [ c2 b2 ]
+                ];
+                b = matDet [
+                    [ a1 c1 ]
+                    [ a2 c2 ]
+                ];
+            };
+            denominator = matDet [
+                [ a1 b1 ]
+                [ a2 b2 ]
+            ];
+        }) mathified;
+    tokens = (
+        lib.lists.foldr
+            ({ numerators, denominator }: accumulated-tokens:
+                accumulated-tokens + (
+                    if (
+                        (lib.trivial.mod numerators.a denominator) != 0
+                        || (lib.trivial.mod numerators.b denominator) != 0
+                    )
+                    then 0
+                    else (numerators.a / denominator) * 3 + (numerators.b / denominator)
+                )
+            )
+            0
+    ) determinants;
+
+    output = tokens;
+in output
\ No newline at end of file