Bump Rust version to 1.86

Author: maneatingape

.github/workflows/checks.yml

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
-    - run: rustup default 1.85
+    - run: rustup default 1.86
     - run: cargo test
 
   test-nightly:

.github/workflows/docs.yml

@@ -18,7 +18,7 @@ jobs:
       url: ${{ steps.deployment.outputs.page_url }}
     steps:
       - uses: actions/checkout@v4
-      - run: rustup default 1.85
+      - run: rustup default 1.86
       - run: cargo doc
         env:
           RUSTDOCFLAGS: "--document-private-items --default-theme=ayu --deny warnings"

Cargo.toml

@@ -2,7 +2,7 @@
 name = "aoc"
 version = "2024.12.25"
 edition = "2024"
-rust-version = "1.85"
+rust-version = "1.86"
 
 [features]
 frivolity = []

README.md

@@ -138,7 +138,7 @@ Performance is reasonable even on older hardware, for example a 2011 MacBook Pro
 | 2 | [Rock Paper Scissors](https://adventofcode.com/2022/day/2) | [Source](src/year2022/day02.rs) | 3 |
 | 3 | [Rucksack Reorganization](https://adventofcode.com/2022/day/3) | [Source](src/year2022/day03.rs) | 13 |
 | 4 | [Camp Cleanup](https://adventofcode.com/2022/day/4) | [Source](src/year2022/day04.rs) | 8 |
-| 5 | [Supply Stacks](https://adventofcode.com/2022/day/5) | [Source](src/year2022/day05.rs) | 14 |
+| 5 | [Supply Stacks](https://adventofcode.com/2022/day/5) | [Source](src/year2022/day05.rs) | 13 |
 | 6 | [Tuning Trouble](https://adventofcode.com/2022/day/6) | [Source](src/year2022/day06.rs) | 3 |
 | 7 | [No Space Left On Device](https://adventofcode.com/2022/day/7) | [Source](src/year2022/day07.rs) | 14 |
 | 8 | [Treetop Tree House](https://adventofcode.com/2022/day/8) | [Source](src/year2022/day08.rs) | 51 |

src/year2022/day05.rs

@@ -1,8 +1,4 @@
 //! # Supply Stacks
-//!
-//! There are 2 main challenges to this problem:
-//! * Parsing the input!
-//! * (Rust Specific): The borrow checker prevents mutating a nested `vec` at 2 indices at once.
 use crate::util::iter::*;
 use crate::util::parse::*;
 
@@ -61,26 +57,23 @@ pub fn part2(input: &Input) -> String {
     play(input, false)
 }
 
-/// Rust's borrow checker won't allow us to mutate 2 nested `vec`s simulataneously, so we need
-/// to use an temporary intermediate `vec` to store the moving crates. For efficiency we can re-use
-/// the same vec to prevent unnecessary memory allocations.
-///
+/// `get_disjoint_mut` allows us to acquire two simultaneous mutable references to disjoint indices.
 /// A nice standard library feature is that we can collect an iterator of `char`s into a `String`
 /// for the final answer.
 fn play(input: &Input, reverse: bool) -> String {
     let (initial, moves) = input;
     let mut stack = initial.clone();
-    let mut crates = Vec::new();
 
     for &[amount, from, to] in moves {
-        let start = stack[from].len() - amount;
-        crates.extend(stack[from].drain(start..));
+        let [from, to] = stack.get_disjoint_mut([from, to]).unwrap();
+        let start = from.len() - amount;
+        let iter = from.drain(start..);
+
         if reverse {
-            stack[to].extend(crates.iter().rev());
+            to.extend(iter.rev());
         } else {
-            stack[to].extend(crates.iter());
+            to.extend(iter);
         }
-        crates.clear();
     }
 
     stack.iter().map(|v| v.last().unwrap()).collect()