Data update

Task/Permutations/Rust/permutations-2.rs

@@ -0,0 +1,18 @@
+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());
+        }
+    }
+}
+
+fn main() {
+    let mut queue = (1..4).collect::<VecDeque<_>>();
+    permute(&mut Vec::new(), &mut queue, &|perm| println!("{:?}", perm));
+}