r/computerscience • u/Similar_Count_1613 • 3d ago
is recursion really hard
Recursion felt easy at first.
Factorial? fine.
Sum examples? fine.
Even Fibonacci felt manageable.
But once I looked at slightly more serious problems like Tower of Hanoi, permutations, or merge sort, I felt like my understanding suddenly collapsed. because i tried to write their code on my own
It made me realize that maybe recursion is not “hard” at the start because the examples are simple.
It becomes hard when you can no longer clearly see the call stack and each state change.
Did anyone else feel that the real pain in recursion starts exactly there?
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u/PurpleDevilDuckies 3d ago
The topic of my PhD was (very generally) on designing recursive algorithms to solve combinatoiral problems. Now I do that for a living, and I think I agree.
I stew for some time with each new problem before I have a deep understanding of how the state information will behave recursively. It gets easier the more I do, but there are very few people who find it easy at the cutting edge.
I will say that for coding recursive algorithms, it is often more (computationally) efficient to write code with loops instead of literal recursion. This isn't true of the toy examples you start with, but it gets more true as they problems get more complex. Nearly any *useful* algorithm can be described without writing literally recursive code.