CS 115 Lab 14, Part A: Recursion practice

[Back to lab instructions]

Before you start writing your own code, you'll use the the online Python 3 tutor to trace the execution of recursive functions. Try to predict what will happen before stepping through the code in the tutor.

1. Enter the following code into the tutor:

   def mystery(x):
       if x == 0: return 0
       return (x % 10) + mystery(x // 10)
   
   
   def main():
       a = mystery(46213)
   
   
   main()
   

2. Trace through the execution of the function calls, and answer Questions 1 and 2 in your writeup.
3. Enter the following code into the tutor:

   def mystery2(L, i):
       if len(L) <= i: return 0
       return L[i] + mystery2(L, i + 1)
   
   
   def mystery1(L):
       return mystery2(L, 0)
   
   
   def main():
       a = mystery1([4, 10, 1, 3])
   
   
   main()
   

4. Trace through the execution of the function calls, and answer Questions 3 and 4 in your writeup.
5. Continue to Part B.