# Homework 1: Variables & Functions, Control hw01.zip

Due by 11:59pm on Thursday, January 27

## Instructions

Submission: When you are done, submit with ```python3 ok --submit```. You may submit more than once before the deadline; only the final submission will be scored. Check that you have successfully submitted your code on okpy.org. See Lab 0 for more instructions on submitting assignments.

Using Ok: If you have any questions about using Ok, please refer to this guide.

Readings: You might find the following references useful:

Important: The lecture on Monday 1/24 will cover readings 1.3-1.5, which contain the material required for questions 2 and 5. (Control)

Grading: Homework is graded based on correctness. Each incorrect problem will decrease the total score by one point. There is a homework recovery policy as stated in the syllabus. This homework is out of 2 points.

# Required Questions

## Welcome Forms

### Q1: Welcome Forms

Please fill out both the Syllabus Quiz, which is based off of our policies found on the course syllabus, as well as the optional Welcome Survey.

## Parsons Problems

To work on these problems, open the Parsons editor:

``python3 parsons``

### Q2: k in Num

Write a function `k_in_num` which takes in two integers, `k` and `num`. `k_in_num` returns `True` if `num` has the digit `k` and returns `False` if `num` does not have the digit `k`. `0` is considered to have no digits.

``````def k_in_num(k, num):
"""
Complete k_in_num, a function which returns True if num has the digit k and
returns False if num does not have the digit k. 0 is considered to have no
digits.

>>> k_in_num(3, 123) # .Case 1
True
>>> k_in_num(2, 123) # .Case 2
True
>>> k_in_num(5, 123) # .Case 3
False
>>> k_in_num(0, 0) # .Case 4
False
"""
``````

## Code Writing Problems

### Q3: A Plus Abs B

Python's `operator` module defines binary functions for Python's intrinsic arithmetic operators. For example, calling `operator.add(2,3)` is equivalent to calling the expression `2 + 3`; both will return `5`.

Fill in the blanks in the following function for adding `a` to the absolute value of `b`, without calling `abs`. You may not modify any of the provided code other than the two blanks.

``````def a_plus_abs_b(a, b):
"""Return a+abs(b), but without calling abs.

>>> a_plus_abs_b(2, 3)
5
>>> a_plus_abs_b(2, -3)
5
>>> a_plus_abs_b(-1, 4)
3
>>> a_plus_abs_b(-1, -4)
3
"""
if b < 0:
f = _____
else:
f = _____
return f(a, b)``````

Use Ok to test your code:

``python3 ok -q a_plus_abs_b``

### Q4: Two of Three

Write a function that takes three positive numbers as arguments and returns the sum of the squares of the two smallest numbers. Use only a single line for the body of the function.

``````def two_of_three(i, j, k):
"""Return m*m + n*n, where m and n are the two smallest members of the
positive numbers i, j, and k.

>>> two_of_three(1, 2, 3)
5
>>> two_of_three(5, 3, 1)
10
>>> two_of_three(10, 2, 8)
68
>>> two_of_three(5, 5, 5)
50
"""
return _____
``````

Hint: Consider using the `max` or `min` function:

``````>>> max(1, 2, 3)
3
>>> min(-1, -2, -3)
-3``````

Use Ok to test your code:

``python3 ok -q two_of_three``

### Q5: Largest Factor

Write a function that takes an integer `n` that is greater than 1 and returns the largest integer that is smaller than `n` and evenly divides `n`.

``````def largest_factor(n):
"""Return the largest factor of n that is smaller than n.

>>> largest_factor(15) # factors are 1, 3, 5
5
>>> largest_factor(80) # factors are 1, 2, 4, 5, 8, 10, 16, 20, 40
40
>>> largest_factor(13) # factor is 1 since 13 is prime
1
"""
Hint: To check if `b` evenly divides `a`, you can use the expression `a % b == 0`, which can be read as, "the remainder of dividing `a` by `b` is 0."
``python3 ok -q largest_factor``
``python3 ok --submit``