permutation using recursion and three arguments

Question

Python non-fruitful recursive function. Implement such a function print_01_strings(k,s,n) that, given a string s of length k, prints all the possible 0/1 strings that are completions of s to length n in the alphanumeric order. Naturally, when print_01_strings(0,'',n) is called, all the 0/1 strings of length n will be printed.

Use the following pattern to implement your solutions and feel free to use the schema for implementing the function:

def print_01_strings(k, s, n):
 #if k equal to n the function only needs to print s which is unique completion
 #otherwise, we'll print all the completions of the string s+'0' of length k+1
 #and all the completions of the string s+'1' of length k+1

print_01_strings(0,'',5)

I have this question in compsci class and for the life of me I cannot get my head around it. I cannot understand how this should work. the output should be something like;

thank you guys in advance, I know I should show an attempt of code but I truly do not know where to start.

--

Do you understand recursion? If not, please see your course materials that cover recursion. — k_ssb
– k_ssb, Commented Oct 22, 2018 at 8:52
yes, It involves breaking down a big problem to smaller problem then extrapolating. — Farah
– Farah, Commented Oct 22, 2018 at 8:59

k_ssb · Accepted Answer · 2018-10-22 09:08:00Z

3

This is an exercise in recursion. I won't do the assignment entirely for you, but I can point out hints to help you get started.

For reference, here is the function you're supposed to implement:

def print_01_strings(k, s, n):
  # if k equal to n the function only needs to print s which is unique completion
  # otherwise, we'll print all the completions of the string s+'0' of length k+1
  # and all the completions of the string s+'1' of length k+1

The comments tell you what to do:

In the base case ("k equal to n"), you should just "print s".
For the recursive cases ("otherwise, ..."), you'll need to call print_01_strings twice with appropriate arguments.
1. The first call handles "completions of the string s+'0' of length k+1".
2. The second call handles "completions of the string s+'1' of length k+1".

Try to figure out what arguments should be passed to the recursive calls to print_01_strings in each of these cases.

answered Oct 22, 2018 at 9:08

k_ssb

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1 Comment

Farah Over a year ago

thanks for the explanation - it makes much more sense to me now!

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