Data update

Task/N-queens-problem/Rust/n-queens-problem-2.rust

@@ -7,7 +7,7 @@ fn main() {
     }
 }
 
-fn permutations<'a, T, I>(collection: I) -> Box<Iterator<Item=LinkedList<T>> + 'a>
+fn permutations<'a, T, I>(collection: I) -> Box<Iterator<dyn Item=LinkedList<T>> + 'a>
     where I: 'a + IntoIterator<Item=T> + Clone,
           T: 'a + PartialEq + Copy + Clone {
     if collection.clone().into_iter().count() == 0 {
@@ -26,7 +26,7 @@ fn permutations<'a, T, I>(collection: I) -> Box<Iterator<Item=LinkedList<T>> + '
 }
 
 pub struct NQueens {
-    iterator: Box<Iterator<Item=NQueensSolution>>
+    iterator: Box<Iterator<dyn Item=NQueensSolution>>
 }
 
 impl NQueens {

Task/N-queens-problem/Rust/n-queens-problem-3.rust

@@ -0,0 +1,29 @@
+extern crate itertools;
+
+use itertools::Itertools;
+
+fn main() {
+    const N: usize = 8;
+
+    let permutations = (0..N).permutations(N);
+
+    let solution_count = permutations
+        .filter(|p| {
+            let mut diag1 = [false; 2 * N - 1];
+            let mut diag2 = [false; 2 * N - 1];
+
+            for (i, &row) in p.iter().enumerate() {
+                if diag1[row + i] || diag2[N - 1 + row - i] {
+                    return false; // Queens mutual threat
+                }
+
+                diag1[row + i] = true;
+                diag2[N - 1 + row - i] = true;
+            }
+
+            true // No Queens mutual threat
+        })
+        .count();
+
+    println!("{}", solution_count);
+}