# Need explanation of Heap's Algorithm

Okay I am trying to understand the Heap's Algorithm from the original research paper published by B.R Heap.

The most confusing aspect I found that while Heap says that the example described on the first page takes N=12 ie. example with 12 objects to provide a permutations for them.

But yet he says that the 12 objects are the letters A to Q. Now unless I have forgotten my counting totally, A to Q is 17 objects not 12. So am I missing something obvious ?

Secondly, can someone please explain the Table 1 given in the bottom of the first page ?

Thanks.

• We expect references to fulfill the minimal scholarly requirements and be as robust over time as possible. Please take some time to improve your post in this regard. We have collected some advice here. Commented Jul 18, 2016 at 10:32
• Please make your question self-contained by quoting the relevant passages and definitions. Commented Jul 18, 2016 at 10:32

Pay no attention to the letter $Q$. $Q$ is just a "short-hand" for "the $N$th letter". Think of $Q$ as a kind of variable, rather than a letter itself.