From 8acee0934c6a9977436578ec0206a94554bfab11 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hugo=20M=C3=A5rdbrink?= <hugo@mardbrink.se>
Date: Mon, 6 Oct 2025 23:35:38 +0200
Subject: [PATCH] Day 12

---
 d12/main.odin | 151 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 151 insertions(+)
 create mode 100644 d12/main.odin

diff --git a/d12/main.odin b/d12/main.odin
new file mode 100644
index 0000000..99ad457
--- /dev/null
+++ b/d12/main.odin
@@ -0,0 +1,151 @@
+package main
+
+import "core:unicode/utf8"
+import "core:math"
+import "core:slice"
+import "core:strconv"
+import "core:strings"
+import "core:bytes"
+import "core:fmt"
+import "core:os"
+
+import "../util"
+
+Type :: enum {
+    East,
+    North,
+    West,
+    South,
+
+    Left,
+    Right,
+
+    Forward
+}
+
+Instruction :: struct {
+    type: Type,
+    units: int,
+}
+
+part_1 :: proc(lines: []string) {
+    result := 0
+    
+    instructions := slice.mapper(lines, proc(line: string) -> (instruction: Instruction) {
+        switch line[0] {
+        case 'N': instruction.type = .North
+        case 'S': instruction.type = .South
+        case 'E': instruction.type = .East 
+        case 'W': instruction.type = .West
+        case 'L': instruction.type = .Left
+        case 'R': instruction.type = .Right
+        case 'F': instruction.type = .Forward
+        }
+
+        ok: bool
+        instruction.units, ok = strconv.parse_int(line[1:]); assert(ok)
+        return instruction
+    })
+
+    direction := Type.East
+    location := [2]int{}
+    for instruction in instructions {
+        switch instruction.type {
+        case .North: location.y += instruction.units
+        case .South: location.y -= instruction.units
+
+        case .East: location.x += instruction.units
+        case .West: location.x -= instruction.units
+
+        case .Left:
+            turn_units := instruction.units / 90
+            direction_int := (int(direction) + turn_units) % 4
+            direction = Type(direction_int)
+        case .Right:
+            turn_units := instruction.units / 90
+            direction_int := (int(direction) - turn_units + 4) % 4
+            direction = Type(direction_int)
+
+        case .Forward: 
+            #partial switch direction {
+            case .North: location.y += instruction.units
+            case .South: location.y -= instruction.units
+            case .East: location.x += instruction.units
+            case .West: location.x -= instruction.units
+            }
+        }
+    }
+    
+    result = abs(location.x) + abs(location.y) 
+    fmt.printfln("Part 1: %d", result)
+}
+
+part_2 :: proc(lines: []string) {
+    result := 0
+    
+    instructions := slice.mapper(lines, proc(line: string) -> (instruction: Instruction) {
+        switch line[0] {
+        case 'N': instruction.type = .North
+        case 'S': instruction.type = .South
+        case 'E': instruction.type = .East 
+        case 'W': instruction.type = .West
+        case 'L': instruction.type = .Left
+        case 'R': instruction.type = .Right
+        case 'F': instruction.type = .Forward
+        }
+
+        ok: bool
+        instruction.units, ok = strconv.parse_int(line[1:]); assert(ok)
+        return instruction
+    })
+
+    ship_location := [2]int{ 0, 0 }
+    waypoint_location := [2]int{ 10, 1 }
+    for instruction in instructions {
+        switch instruction.type {
+        case .North: waypoint_location.y += instruction.units
+        case .South: waypoint_location.y -= instruction.units
+
+        case .East: waypoint_location.x += instruction.units
+        case .West: waypoint_location.x -= instruction.units
+
+        case .Left: 
+            turns := instruction.units / 90
+            for _ in 0..<turns {
+                x := waypoint_location.x
+                y := waypoint_location.y
+
+                waypoint_location.y = x
+                waypoint_location.x = -y
+            }
+        case .Right:
+            turns := instruction.units / 90
+            for _ in 0..<turns {
+                x := waypoint_location.x
+                y := waypoint_location.y
+
+                waypoint_location.y = -x
+                waypoint_location.x = y
+            }
+
+        case .Forward: 
+            ship_location.x += instruction.units * waypoint_location.x
+            ship_location.y += instruction.units * waypoint_location.y
+        }
+    }
+    
+    result = abs(ship_location.x) + abs(ship_location.y) 
+    fmt.printfln("Part 2: %d", result)
+}
+
+main :: proc() {
+    context.allocator = context.temp_allocator
+    defer free_all(context.temp_allocator)
+
+    INPUT :: #load("input.txt", string)
+    lines := strings.split(INPUT, "\n")
+    lines = lines[:len(lines)-1]
+
+    part_1(lines)
+    part_2(lines)
+}