From 28178c8a73b93cc7befbae8527f371afd307dffe Mon Sep 17 00:00:00 2001
From: Bert Peters <bert@bertptrs.nl>
Date: Fri, 1 Dec 2023 10:22:26 +0100
Subject: [PATCH] Slightly more natural part 1

---
 2023/src/day01.rs | 24 ++++++++++--------------
 1 file changed, 10 insertions(+), 14 deletions(-)

diff --git a/2023/src/day01.rs b/2023/src/day01.rs
index f783805..b1f7ef2 100644
--- a/2023/src/day01.rs
+++ b/2023/src/day01.rs
@@ -1,12 +1,5 @@
 use anyhow::Result;
 
-fn to_digit(c: u8) -> Option<u32> {
-    match c {
-        b'0'..=b'9' => Some(u32::from(c - b'0')),
-        _ => None,
-    }
-}
-
 pub fn part1(input: &[u8]) -> Result<String> {
     let mut it = input.iter();
     let mut sum = 0;
@@ -15,13 +8,16 @@ pub fn part1(input: &[u8]) -> Result<String> {
         let mut first = None;
         let mut last = 0;
 
-        for digit in it
-            .by_ref()
-            .take_while(|&&c| c != b'\n')
-            .filter_map(|&c| to_digit(c))
-        {
-            first.get_or_insert(digit);
-            last = digit;
+        for &c in &mut it {
+            match c {
+                d @ b'0'..=b'9' => {
+                    let digit = u32::from(d - b'0');
+                    first.get_or_insert(digit);
+                    last = digit;
+                }
+                b'\n' => break,
+                _ => continue,
+            }
         }
 
         if let Some(first) = first {