fix: check duplicated pieces (#11)

kewb/src/cube/cubie.rs

@@ -1,7 +1,7 @@
 use self::{Corner::*, Edge::*, Move::*};
 use crate::error::Error;
 
-use super::{facelet::*, moves::*};
+use super::{facelet::*, moves::*, utils::has_duplicates};
 use std::ops::Mul;
 
 /// Represents the 8 corners on the cube, described by the layer they are on.
@@ -191,6 +191,10 @@ impl CubieCube {
 
     /// Checks if CubieCube is a valid cubie representation.
     pub fn is_solvable(&self) -> bool {
+        if has_duplicates(&self.cp) || has_duplicates(&self.ep) {
+            return false;
+        }
+
         let c_perm = self.count_corner_perm();
         let e_perm = self.count_edge_perm();
         let c_twist = self.count_corner_twist();

kewb/src/cube/mod.rs

@@ -5,3 +5,4 @@ pub mod generators;
 pub mod index;
 pub mod moves;
 pub mod scramble;
+mod utils;

kewb/src/cube/utils.rs

@@ -0,0 +1,6 @@
+pub fn has_duplicates<T: PartialEq>(items: &[T]) -> bool {
+    items
+        .iter()
+        .enumerate()
+        .any(|(i, item)| items[i + 1..].contains(item))
+}