Iter mutably on cycles in advance

Author: Philippe-Cholet

src/permutations.rs

@@ -133,16 +133,15 @@ where
 
 fn advance(indices: &mut [usize], cycles: &mut [usize]) -> bool {
     let n = indices.len();
-    let k = cycles.len();
     // NOTE: if `cycles` are only zeros, then we reached the last permutation.
-    (0..k).rev().all(|i| {
-        if cycles[i] == 0 {
-            cycles[i] = n - i - 1;
+    cycles.iter_mut().enumerate().rev().all(|(i, c)| {
+        if *c == 0 {
+            *c = n - i - 1;
             indices[i..].rotate_left(1);
             true
         } else {
-            indices.swap(i, n - cycles[i]);
-            cycles[i] -= 1;
+            indices.swap(i, n - *c);
+            *c -= 1;
             false
         }
     })