Recursion becomes much easier once students have the right mental model. Visualization will help get them there.

Take the Tower of Hanoi problem. The recursive solution is beautifully short, to move n disks we:

• first remove n-1 disks from the largest disk
• then move the largest disk
• and then move the n-1 disks back on top

But when students try to implement recursion, they often get stuck, and adding debug prints only adds to the confusion. That is where visualization can help to bring the right mental model. Here is the Tower of Hanoi problem solved recursively, visualized with 𝗶𝗻𝘃𝗼𝗰𝗮𝘁𝗶𝗼𝗻_𝘁𝗿𝗲𝗲: https://www.invocation-tree.com/#codeurl=https%3A%2F%2Fraw.githubusercontent.com%2Fbterwijn%2Fmemory_graph_examples%2Frefs%2Fheads%2Fmain%2Ftowers_of_hanoi.py&timestep=0.5&play=

Instead of thinking about “a function calling itself again and again” students can now see the depth-first execution of a tree of subproblems showing the divide-and-conquer strategy in action. Once a student can think in terms of a tree of subproblems, recursion becomes much easier to understand, explain, and debug.

#Python #invocation_tree #Recursion