# Homework 1: Variables & Functions, Control

*Due by 11:59pm on Thursday, January 27*

## Instructions

Download hw01.zip.

**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
"""
"*** YOUR CODE HERE ***"
```

## 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
"""
"*** YOUR CODE HERE ***"
```

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."

Use Ok to test your code:

`python3 ok -q largest_factor`

## Submit

Make sure to submit this assignment by running:

`python3 ok --submit`