From 8ac1df5a0ca7cf52e0d4be5c9724845a0be5a10c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hugo=20M=C3=A5rdbrink?= <hugo@mardbrink.se>
Date: Sun, 5 Oct 2025 20:42:55 +0200
Subject: [PATCH] Day 9

---
 d09/main.odin | 101 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 d09/main.odin

diff --git a/d09/main.odin b/d09/main.odin
new file mode 100644
index 0000000..989fed1
--- /dev/null
+++ b/d09/main.odin
@@ -0,0 +1,101 @@
+package main
+
+import "core:math"
+import "core:slice"
+import "core:strconv"
+import "core:strings"
+import "core:bytes"
+import "core:fmt"
+import "core:os"
+
+import "../util"
+
+PREAMBLE_LEN :: 25 
+
+is_sum_of_two :: proc(target_number: i64, numbers: []i64) -> bool {
+    for num1, idx in numbers {
+        for num2 in numbers[idx+1:] {
+            if num1 + num2 == target_number do return true
+        }
+    }
+
+    return false
+}
+
+part_1 :: proc(lines: []string) {
+    result: i64 = 0
+    
+    numbers := make([]i64, len(lines))
+
+    for line, idx in lines {
+        ok: bool
+        numbers[idx], ok = strconv.parse_i64(line); assert(ok)
+    }
+
+    idx := PREAMBLE_LEN
+    for number in numbers[PREAMBLE_LEN:] { 
+        if !is_sum_of_two(number, numbers[idx-PREAMBLE_LEN:idx]) {
+            result = number
+            break
+        }
+        idx += 1
+    }
+
+    fmt.printfln("Part 1: %d", result)
+}
+
+part_2 :: proc(lines: []string) {
+    result: i64 = 0
+    
+    numbers := make([]i64, len(lines))
+
+    for line, idx in lines {
+        ok: bool
+        numbers[idx], ok = strconv.parse_i64(line); assert(ok)
+    }
+
+    invalid_number: i64
+    idx := PREAMBLE_LEN
+    for number in numbers[PREAMBLE_LEN:] { 
+        if !is_sum_of_two(number, numbers[idx-PREAMBLE_LEN:idx]) {
+            invalid_number = number
+            break
+        }
+        idx += 1
+    }
+
+    min_idx: i64 = 0
+    max_idx: i64 = 0
+    outer: for _ in numbers {
+        contiguous_sum: i64 = 0
+        max_idx = min_idx
+        for num in numbers[min_idx:] {
+            contiguous_sum += num
+            if contiguous_sum == invalid_number {
+                max := slice.max(numbers[min_idx:max_idx+1])
+                min := slice.min(numbers[min_idx:max_idx+1])
+                result = max + min
+                break outer
+            } else if contiguous_sum > invalid_number {
+                break
+            }
+            max_idx += 1
+        }
+        min_idx += 1
+    }
+    
+
+    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)
+}