Part 2 solved and working :D

src/main.rs

@@ -18,4 +18,9 @@ fn main() {
         let max_part1 = prob3::solve_part1(file_path);
         println!("Solution for problem 3 part 1: {max_part1}");
     }
+    {
+        let file_path = "prob3_part2.txt";
+        let max_part2 = prob3::solve_part2(file_path);
+        println!("Solution for problem 3 part 1: {max_part2}");
+    }
 }

src/prob3/mod.rs

@@ -19,10 +19,57 @@ pub fn solve_part1(file_path: &str) -> i32 {
             let (first, last) = item.split_at(item.len() / 2);
             let second = last.chars().collect::<HashSet<char>>();
             let intersection = first.chars().collect::<HashSet<char>>();
-            let character = *intersection.intersection(&second).next().unwrap_or(&(0 as char)) as i32;
+            let character = *intersection
+                .intersection(&second)
+                .next()
+                .unwrap_or(&(0 as char)) as i32;
             character_to_code(character)
         })
         .collect::<Vec<i32>>()
         .iter()
         .sum::<i32>()
 }
+
+pub fn solve_part2(file_path: &str) -> i32 {
+    let binding =
+        std::fs::read_to_string(file_path).expect("Please provide a text file as an argument.");
+    let mut iter = binding.lines();
+    binding
+        .lines()
+        .step_by(3)
+        .collect::<Vec<&str>>()
+        .iter()
+        .map(|item| {
+            let common_letter = {
+                let first = &iter
+                    .next()
+                    .expect("Expected a string, not nothing.")
+                    .chars()
+                    .collect::<HashSet<char>>()
+                    & &iter
+                        .next()
+                        .expect("Expected a string, not nothing.")
+                        .chars()
+                        .collect::<HashSet<char>>();
+                &first
+                    & &iter
+                        .next()
+                        .expect("Expected a string, not nothing.")
+                        .chars()
+                        .collect::<HashSet<char>>()
+            };
+            if !common_letter.is_empty() && common_letter.len() > 1 {
+                panic!("Anormal behavior. Must have only 1 element in {common_letter:?}");
+            } else {
+                let unique_letter = *common_letter
+                    .iter()
+                    .last()
+                    .expect("Impossible to have this message else Rust has a problem...")
+                    as i32;
+                character_to_code(unique_letter)
+            }
+        })
+        .collect::<Vec<i32>>()
+        .iter()
+        .sum::<i32>()
+}