Fixed an error

day_10/src/lib.rs

@@ -147,7 +147,7 @@ pub fn part2(input: &str) -> String {
                     // L's cancel F's, J's cancel 7's
                     if count_map[[new_y,x]] != 0 {
                         // We can add either a half or full count
-                        let next_character = std::str::from_utf8(&[input.as_bytes()[new_y*columns + x]]).unwrap().chars().next().unwrap();
+                        let next_character = input.as_bytes()[new_y*(columns+1) + x] as char;
                         if ['7', 'S'].contains(&next_character) {
                             count_7 += 1;
                         } else if next_character == 'J' {