September 2017 Update

Task/Permutations/Rust/permutations-2.rust

@@ -0,0 +1,25 @@
+use std::collections::VecDeque;
+fn permute<T, F: Fn(&[T])>(used: &mut Vec<T>, unused: &mut VecDeque<T>, action: &F) {
+    if unused.is_empty() {
+        action(used);
+    } else {
+        for _ in 0..unused.len() {
+            used.push(unused.pop_front().unwrap());
+            permute(used, unused, action);
+            unused.push_back(used.pop().unwrap());
+        }
+    }
+}
+
+// Same as the vec! macro, but for VecDeques as well
+macro_rules! vec_deque {
+    ($($item:expr),*) => {{
+        let mut deque = ::std::collections::VecDeque::new();
+        $(deque.push_back($item);)*
+        deque
+    }}
+}
+
+fn main() {
+    permute(&mut Vec::new(), &mut vec_deque![1,2,3], &|perm| println!("{:?}", perm));
+}