Questions about objects such as functions, algorithms or data structures that are expressed using "smaller" instances of themselves.
Questions tagged [recursion]
595 questions
8
votes
2 answers
Difference between Tail-Recursion and structural recursion
Is there any difference between structural-recursion and Tail-recursion or they both are same? I see that in both of these recursions , the recursive function is called on the subset of the orignal items.
Khan Saab
- 253
- 2
- 8
4
votes
1 answer
Recursion Davis' Staircase understanding
I'm going through a hackerrank challenge on recursion https://www.hackerrank.com/challenges/ctci-recursive-staircase
and I'm having difficulty understanding how the solution below solves the problem. Here's the tree (the recursion calls) like you…
user75512
- 41
- 1
- 2
3
votes
1 answer
Is there any practical application for arrays that contain themselves?
I'm reading the introduction to Godel, Escher, Bach and and there's heavy discussion of mathematical sets which contain themselves. Being a far better programmer than mathematician, I put it into terms I'm more comfortable with and started to think…
davidlav
- 143
- 3
3
votes
0 answers
Axiomatisation in the presence of recursion
I read Klaus Havelund's thesis on the Fork Calculus:
http://havelund.com/Publications/thesis.ps
He develops the Fork calculus for reasoning about concurrent functional programs, the motivation being Concurrent ML.
In chapter 5, he writes:
First, we…
Gergely
- 379
- 1
- 9
2
votes
2 answers
Tasks in which recursion is either the fastest or only way to produce a result
I've just finished studying recursion at university. One thing that stood out for me however was that in both the lectures and in the practical we completed, all the tasks we were asked to do could be performed faster, and in less code, using…
Andrew Martin
- 123
- 4
2
votes
1 answer
Integer log2 as a catamorphism?
Recursion schemes are structured methods for expressing recursive functions, of increasing interest due to their ubiquity in functional programming. For example, catamorphisms (familiar in the guise of 'fold' on lists) can be defined for all…
NietzscheanAI
- 817
- 4
- 10
2
votes
1 answer
Decimal to Binary converter with a flaw
Hi I wrote the following recursive decimal to binary function while studying for Andela.
def binary_converter(q):
if q>255 or not isinstance(q, int) or q<0:
return "Invalid input"
if q==0:
return '0'
elif q!=0:
q,…
Jonathan
- 123
- 5
2
votes
0 answers
How to prove νX. A × X ≅ (μX. 1 + X) -> A?
How can we prove Stream A = νX. A × X is isomorphic to Nat -> A = (μX. 1 + X) -> A ?
In programming sense, Stream A can be seen as a function from Nat to A, and I can write isomorphisms between them.
But how can this be proven mathematically?
I…
inamiy
- 121
- 3
2
votes
1 answer
Is this an example of Tail Recursion
As I have read in this answer: What is tail recursion? tail recursion is a special case of recursion where the calling function does no more computation after making a recursive call.
Here after the recursive call we just assign the result to…
Tommaso Bendinelli
- 121
- 2
2
votes
1 answer
How does this recursive algorithm work?
One question from the Grokking Algorithms book:
Implement a max([]int) function, returning the biggest element in the array.
Here's my solution in Golang (adapted from the Python solution in the book):
func maxNumber(arr []int) (r int) {
// base…
jonatasbaldin
- 23
- 2
2
votes
1 answer
Is there purely recursive functions?
Is there any problem that can be only solved with recursion, and not with iteration? (haven't been able to find anything online).
If there isn't any, is there a reason why?
Thanks in advance!
Mason Hawver
- 23
- 2
1
vote
1 answer
Towers of Hanoi Algorithm "Using Auxiliary" Peg
I'm trying to fully understand how the recursive Towers of Hanoi Algorithm works and to implement it in code.
Something that keeps throwing me of is the use of phrases like "move n-1 discs from A to B using C."
I understand that the peg which is…
Robin Andrews
- 255
- 2
- 14
1
vote
1 answer
Converting Recursion into Into Iteration
While reading Code Complete second edition, I came across this line:
You can do anything with stacks and iteration that you can do with
recursion.
Is this true? or there are functions, that must be implemented recursively, and can't be done…
Bite Bytes
- 249
- 1
- 7
1
vote
3 answers
Value returned by recursive function
(pseudocode)
f(x,y,z)
{
if (x < y)
{
return 1 + f(x + 1, y, z)
}
else if (y < z)
{
return 2 + f(x, y + 1, z)
}
else
{
return z
}
}
The function call f(12,14,20) returns $40$. Why is…
Marcel
- 133
- 4
1
vote
3 answers
Having trouble on logic behind recursion
I am struggling to write my own recursive function.I understand how to find the base case but I cant find easily the pattern on the relationship between 2 complicated cases.Do you know any website where I can practice that?
Cerise
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