clean up 16

day16/Cargo.toml

@@ -5,3 +5,6 @@ edition = "2024"
 
 [dependencies]
 itertools = "*"
+
+[profile.release]
+debug = true

day16/src/main.rs

@@ -19,16 +19,14 @@ fn main() {
 fn calculate_checksum(length: usize) {
     let mut a = INPUT.to_string();
     while a.len() < length {
-        let mut b = a.clone();
-        b = b
-            .chars()
-            .rev()
-            .map(|c| if c == '0' { '1' } else { '0' })
-            .collect();
+        let b = a.clone();
+        let b_chars = b.chars().rev().map(|c| if c == '0' { '1' } else { '0' });
 
         let mut result = a.clone();
         result.push('0');
-        result.push_str(&b);
+        for ch in b_chars {
+            result.push(ch);
+        }
         a = result;
     }
     a.truncate(length);