moved code around so each year is a package.

core/Cargo.toml

@@ -0,0 +1,4 @@
+[package]
+name = "core"
+version = "0.1.0"
+edition = "2024"

core/src/bin/test.rs

@@ -0,0 +1,20 @@
+fn num_to_change(input: &str) -> usize {
+    let mut return_value = 0;
+    let mut last_char = '\0';
+
+    for (index, current_char) in input.chars().enumerate() {
+        if index != 0 {
+            if last_char != current_char {
+                return_value = index;
+                break
+            }
+        }
+        last_char = current_char
+    }
+    return_value
+}
+
+fn main () {
+    assert_eq!(num_to_change("01234567"), 1);
+    assert_eq!(num_to_change("00000000001"), 10);
+}

core/src/lib.rs

@@ -0,0 +1,58 @@
+use std::io::{stdout, Write};
+
+/// AOC Lib
+/// Generic methods for loading various data inputs from
+/// the AOC project.
+
+pub fn data_path(suffix: &str) -> String {
+    let path = std::env::var("CARGO_MANIFEST_DIR").unwrap();
+    stdout().flush().unwrap();
+    format!("{}/../data/{}", path, suffix)
+}
+
+pub fn read_data(suffix: &str) -> String {
+    std::fs::read_to_string(
+        data_path(suffix)
+    ).unwrap()
+}
+
+pub fn string_to_3u32(input: &str) -> Option<(u32, u32, u32)> {
+    let parts: Vec<&str> = input.split('x').collect();
+    if parts.len() == 3 {
+        if let (Ok(a), Ok(b), Ok(c)) = (
+            parts[0].parse::<u32>(),
+            parts[1].parse::<u32>(),
+            parts[2].parse::<u32>(),
+        ) {
+            return Some((a, b, c));
+        }
+    }
+    None
+}
+
+pub fn largest_of_vec(to_check: &Vec<u32>) -> u32 {
+    let mut working = to_check[0];
+    for current in to_check {
+        if current > &working {
+            working = *current
+        }
+    }
+    working
+}
+pub fn smallest_of_vec(to_check: &Vec<u32>) -> u32 {
+    let mut working = to_check[0];
+    for current in to_check {
+        if current < &working {
+            working = *current
+        }
+    }
+    working
+}
+
+pub fn sum_of_vec(to_add: &Vec<u32>) -> u32 {
+    let mut working = 0;
+    for current in to_add {
+        working += current
+    }
+    working
+}