At outer loop node 1, we'd inner loop through 1.

At outer loop node 3, we'd inner loop through 1 -> 3.

At outer loop node 5, we'd inner loop through 1 -> 3 -> 5.

At outer loop node 3 again, we'd inner loop through 1 -> 3 -> 5 -> 3.

So the brute force way to do it is to conduct a nested traversal-- we can traverse all the nodes, and then at each iteration, traverse through the nodes already visited by the outer loop. In the inner loop, if we encounter a node twice, we know it's been repeated.