Commit d78517f4f0

@@ -61,6 +61,20 @@ pub fn SinglyLinkedList(comptime T: type) type {
                 }
                 return count;
             }
+
+            /// Invert the list starting from this node in-place.
+            /// This operation is O(N).
+            pub fn invert(indirect: *?*Node) void {
+                if (indirect.* == null) {
+                    return;
+                }
+                var current: *Node = indirect.*.?;
+                while (current.next) |next| {
+                    current.next = next.next;
+                    next.next = indirect.*;
+                    indirect.* = next;
+                }
+            }
         };
 
         first: ?*Node = null,
@@ -149,6 +163,12 @@ test "basic SinglyLinkedList test" {
     try testing.expect(list.first.?.data == 2);
     try testing.expect(list.first.?.next.?.data == 4);
     try testing.expect(list.first.?.next.?.next == null);
+
+    L.Node.invert(&list.first);
+
+    try testing.expect(list.first.?.data == 4);
+    try testing.expect(list.first.?.next.?.data == 2);
+    try testing.expect(list.first.?.next.?.next == null);
 }
 
 /// A tail queue is headed by a pair of pointers, one to the head of the