Detect ECB via duplicated chunks instead of Hemming distance as I should have done in the first place.

src/set1.rs

@@ -193,17 +193,28 @@ pub fn challenge8() {
         rating
     }
 
+    let expected_index: usize = 132;
     let bytes_vector = read("data/8.txt");
     let ratings: Vec<u32> = bytes_vector.iter().map(|b| rate(&b, 16)).collect();
     let min_rating = ratings.iter().min().unwrap();
     let index = ratings.iter().position(|e| e == min_rating).unwrap();
     let average = ratings.iter().sum::<u32>() as f32 / ratings.len() as f32;
     let partial_cipher = bytes_vector[index].to_hex()[..10].to_string();
-    if index != 132 {
+    if index != expected_index {
         panic!("Regression in challenge 8.");
     }
     println!(
         "[okay] Challenge 8: Cipher {} [{}...] with rating {} (average = {}) is the solution.",
         index, partial_cipher, min_rating, average
     );
+
+    // More elegant solution.
+    let bytes_vector = read("data/8.txt");
+    let ix: Vec<usize> = bytes_vector
+        .iter()
+        .enumerate()
+        .filter(|&(_, bytes)| bytes.has_duplicated_cycle(16))
+        .map(|(i, _)| i)
+        .collect();
+    assert_eq!(ix[0], expected_index);
 }