gateway 2

Question 1

def foo(arr, n):
if n== 0:
return 0
else:
return foo(arr, n-1) + arr[n-1]

example = np.array([2, 6, 8, 1, 4])
print(foo(example, example.size))

Answer 1

21

Question 2

def dunno(word: str, n: int):
if n == 1:
print(word)
else:
print(word, end = “ “)
dunno(word, n-1)

dunno(“yes”, 5)

Answer 2

yes yes yes yes yes

Question 3

def fun(x, y) :
if (x == 0) :
return y
else :
return fun(x - 1, x + y)

print(fun(3, 10))

Answer 3

16

Question 4

Assume that n is greater than or equal to 1
def mystery(n):
if(n == 1):
return 0
else:
return 1 + mystery(n//2)

print(mystery(1))
print(mystery(5))
print(mystery(17))

Answer 4

0
2
4

Question 5

Assume that n is greater than or equal to 0 */
def something(n):
if(n == 0):
return
else:
something(n // 2)
print(n % 2, end=””)

something(1)
something(5)
something(9)

Answer 5

11011001

Question 6

Write a function called is_power_of_two that takes a positive integer as input and returns a bool. Return True if the value passed is a power of 2, and False otherwise

Answer 6

def is_power_of_two(n):
if n == 1:
return True
elif n % 2 != 0 or n == 0:
return False
else:
return is_power_of_two(n // 2)

Question 7

Write a recursive function called print_triangle that takes an integer parameter (you may assume without checking that it is an integer greater than or equal to 1). Print the following triangle pattern, where the number of lines is determined by the value of the parameter.

**
*

Answer 7

def print_triangle(n):
if n == 0:
return
print(“*” * n)
print_triangle(n - 1)

Question 8

Finally, modify the code minimally so that it prints this pattern instead:

*
**
**
**
**

Answer 8

def print_triangle(n):
if n == 6:
return
print(“*” * n)
print_triangle(n + 1)

Question 9

Write a recursive function called count_down() that takes an integer as a parameter. It should output the integers starting at that value, down to a final value of 1.

Answer 9

def count_down(n):
if n == 1:
print(n)
else:
print(n)
count_down(n - 1)

Question 10

Then modify the code slightly to implement a recursive count_up() function.

Answer 10

def count_up(n):
if n == 1:
print(n)
else:
count_up(n - 1)
print(n)

Question 11

Write a recursive function called sum_1_to_n() that takes an integer parameter and returns the sum of the integers from 1 up to the parameter passed.

Answer 11

def sum_1_to_n(n):
if n <= 0:
return 0
else:
return n + sum_1_to_n(n - 1)

Question 12

Write a recursive function called recursive_pow() that takes two parameters. The first is the base, and the second is an integer exponent.

Answer 12

def recursive_pow(base, exponent):
if exponent == 0:
return 1
elif exponent > 0:
return base * recursive_pow(base, exponent - 1)
else:
return 1 / recursive_pow(base, -exponent)

Question 13

import copy

class ThreeNumbers:

def \_\_init\_\_(self, n1: float, n2: float, n3: float):
	self.number1 = n1
	self.number2 = n2
	self.number3 = n3

def main():
object1 = ThreeNumbers(2, 3.14159, 2.71828)
object2 = object1
object3 = copy.copy(object1)
object1.number1 = 9
object2.number1 = 47
print(object1)
print(object2)
print(object3)
print(object1.number1, object2.number1, object3.number1)

if __name__ == “__main__”:
main()

T/F Line 12 copies a reference (memory address)

Answer 13

truth

Question 14

import copy

class ThreeNumbers:

def \_\_init\_\_(self, n1: float, n2: float, n3: float):
	self.number1 = n1
	self.number2 = n2
	self.number3 = n3

def main():
object1 = ThreeNumbers(2, 3.14159, 2.71828)
object2 = object1
object3 = copy.copy(object1)
object1.number1 = 9
object2.number1 = 47
print(object1)
print(object2)
print(object3)
print(object1.number1, object2.number1, object3.number1)

if __name__ == “__main__”:
main()

T/F Line 13 performs a deep copy

Answer 14

false

Question 15

import copy

class ThreeNumbers:

def \_\_init\_\_(self, n1: float, n2: float, n3: float):
	self.number1 = n1
	self.number2 = n2
	self.number3 = n3

def main():
object1 = ThreeNumbers(2, 3.14159, 2.71828)
object2 = object1
object3 = copy.copy(object1)
object1.number1 = 9
object2.number1 = 47
print(object1)
print(object2)
print(object3)
print(object1.number1, object2.number1, object3.number1)

if __name__ == “__main__”:
main()

T/F Lines 16-18 output a memory address since __str__ was not implemented in the class ThreeNumbers.

Answer 15

truth

Question 16

import copy

class ThreeNumbers:

def \_\_init\_\_(self, n1: float, n2: float, n3: float):
	self.number1 = n1
	self.number2 = n2
	self.number3 = n3

def main():
object1 = ThreeNumbers(2, 3.14159, 2.71828)
object2 = object1
object3 = copy.copy(object1)
object1.number1 = 9
object2.number1 = 47
print(object1)
print(object2)
print(object3)
print(object1.number1, object2.number1, object3.number1)

if __name__ == “__main__”:
main()

What does line 19 output?

Answer 16

47 47 2

Question 17

Write a block of python code that creates a list called rectangles. The list should contain 100 Rectangle objects, whose centers are (0, 0), (0.01, 0.01), (0.02, 0.02), …(0.99, 0.99). The half-width and half-height of each rectangle is 0.01. Then write a block of code that draws all 100 rectangles in the list.

Answer 17

rectangles = []
for i in range(100):
cx = i * 0.01
cy = i * 0.01
rectangle = Rectangle(cx, cy, 0.01, 0.01)
rectangles.append(rectangle)

Draw all 100 rectangles in the list
for rectangle in rectangles:
rectangle.draw()

Question 18

Write a block of code that creates a list that contains 366 Date objects, one for every day in 2024.

Answer 18

dates = []
for month in range(1, 13):
days_in_current_month = Date.days_in_month_ly if Date(month).is_leap_year() else Date.days_in_month[month - 1]
for day in range(1, days_in_current_month + 1):
date = Date(month, day, 2024)
dates.append(date)

Question 19

Write a __lt__ method for the Date class that determines if one Date precedes another Date in time

Answer 19

def __lt__(self, other):
if self.year < other.year:
return True
elif self.year > other.year:
return False
else:
if self.month < other.month:
return True
elif self.month > other.month:
return False
else:
return self.day < other.day

Question 20

For the Rectangle class defined in question 1, add code so that == returns True when the center and dimensions of two rectangles are all the same, and False otherwise.

Answer 20

def __eq__(self, other):
if isinstance(other, Rectangle):
return (
self.x == other.x and
self.y == other.y and
self.width == other.width and
self.height == other.height
)
return False

Question 21

What is output by the following code?

class ExampleClass:
cvn = 0
cvc = 0
cvp = 1

Answer 21

28
20
28 2 5 8
20 2 5 8