Implement challenge 33 Diffie-Hellman

src/set3.rs

@@ -186,7 +186,7 @@ mod challenge19 {
 
             for i in 0..ciphers_len {
                 for j in i..ciphers_len {
-                    if target_bytes[i] == None || target_bytes[j] == None {
+                    if target_bytes[i].is_none() || target_bytes[j].is_none() {
                         continue;
                     }
                     let xored = target_bytes[i].unwrap() ^ target_bytes[j].unwrap();