COSC 350: Data Structures
Practice Problems for Recursion
These problems will not be collected or graded. They are provide simply to give you
practice. Most are of a difficulty such that you should be able to solve one on a class
quiz. In each case you should write a recursive function to complete the
1. Addition can be implemented using just an increment and a decrement function,
functions that add and subtract one. You increment one number will
decrementing another until the decremented number is zero.
2. Multiplication can be implemented using repeated additions.
3. Division can be implemented using repeated subtractions.
4. Exponentiation can be implemented using repeated multiplications.
5. Any sort of while-loop can be rewritten as a recursive function. Find examples of
while-loops and practice rewriting them.
6. Any sort of for-loop can be rewritten as a recursive function. Find examples of
for-loops and practice rewriting them.
7. As the course progresses, we will see that lists can be thought of a recursive
structures. But you already know enough to write some list operations recursively
using Python’s built-in lists. Write a function to count the number of items in a
list.
8. Write a function to add one to each item in a list of numbers.
9. Write a function to multiply by two each item in a list of numbers.
10. Write a function to map a function over items in a list, i.e., apply the function to
each item in the list. E.g., map(abs, [1,–2, 3, –4, –5]) would return [1, 2,
3, 4, 5].
11. Write a function to print the elements in a list in order. Then change the function
so that the list is printed in reverse order. You should only need to make one
change in the order of the statements in the function.
12. Rewrite the previous function using strings.
13. Write a function that returns the reverse of a list. … of a string.
