Problem 292. Infernal Recursion

Created by Matt Fig

Solve Later

Consider the recursion relation:

x_n = (x_(n-1)*x_(n-2))^k

Given x_1, x_2, and k, x_n can be found by this definition. Write a function which takes as input arguments x_1, x_2, n and k. The output should be x_n.

For example, if x_1=exp(1), x_2=pi, n=5, and k=5/9 then:

R = get_recurse(exp(1),pi,5,4/9)

R =
      2.31187497992966

Solve

Solution Stats

145 Solutions
67 Solvers

Last Solution submitted on May 20, 2020

Last 200 Solutions

Problem Comments

4 Comments

4 Comments

Show 1 older comment

@bmtran (Bryant Tran) on 9 Feb 2012

is there a story as to why this is "infernal"?

Matt Fig on 9 Feb 2012

I hate recursion, so it is all infernal to me! Iteration is the way to go...

David Young on 29 Feb 2012

Test suite could helpfully include n=1 and n=2 tests. I thought that it needed extra complexity to handle these, but @bmtran's top solution shows it doesn't.

Aurelien Queffurust on 12 Jun 2012

I spend a lot of time to get the correct R from the example. The issue is that you say k = 5/9 instead of 4/9 . Just a typo to correct . Thanks

Solution Comments

Solution 654037

2 Comments

2 Comments

bainhome on 16 Apr 2015

cheat this one because I think my answer wasn't wrong despite the stupidity, wonder if why this insanely slow.

bainhome on 16 Apr 2015

"Recursion" in title had me in a really tricky detour.

Solution 86964

1 Comment

1 Comment

Binbin Qi on 9 May 2012

it cost much too time,so .....

Solution 37119

1 Comment

1 Comment

David Young on 29 Feb 2012

Fails for both n=1 and n=2?

Solution 34698

2 Comments

2 Comments

@bmtran (Bryant Tran) on 9 Feb 2012

holy moly, you posted this one mere seconds after i posted mine.

David Young on 29 Feb 2012

Fails for n=1?

Solution 34697

2 Comments

2 Comments

Alfonso Nieto-Castanon on 9 Feb 2012

that was a photo-finish :)

David Young on 29 Feb 2012

OK for both n=1 and n=2.

Problem Recent Solvers67

Problem Tags

recursion