2021: day02: use split_once

std::cmp::Ord::clamp can't really help in this situation, not sure what
I had in mind

aoc2020/src/day23.rs

@@ -71,8 +71,6 @@ impl CupCircle {
         // keep subtracting one until it finds a cup that wasn't just picked up. If at any point in
         // this process the value goes below the lowest value on any cup's label, it wraps around to
         // the highest value on any cup's label instead.
-        //
-        // TODO: use std::cmp::Ord::clamp when stabilized (Rust 1.50)
         let mut destination = if current > 1 { current - 1 } else { self.max() };
         while removed_cups.contains(&destination) {
             destination = if destination > 1 {
@@ -193,8 +191,6 @@ impl FastCupCircle {
         // keep subtracting one until it finds a cup that wasn't just picked up. If at any point in
         // this process the value goes below the lowest value on any cup's label, it wraps around to
         // the highest value on any cup's label instead.
-        //
-        // TODO: use std::cmp::Ord::clamp when stabilized (Rust 1.50)
         let mut destination = if self.current > 1 {
             self.current - 1
         } else {

aoc2021/src/day02.rs

@@ -69,10 +69,7 @@ impl std::str::FromStr for Command {
     type Err = anyhow::Error;
 
     fn from_str(s: &str) -> Result<Self> {
-        let mut split = s.split(' ');
-
-        let word = split.next().context("couldn't find word in command")?;
-        let number = split.next().context("couldn't find number in command")?;
+        let (word, number) = s.split_once(' ').context("couldn't split command")?;
 
         let number = number.parse()?;