Solutions to ICP1 Homework 2

icp-hw2-solutions.py

"""
Introdcution to Computer Programming 1
Homework 2 Solutions
Advait Shinde

Note: I tried to keep my solutions well documented. Notice the
triple quote documentation in each function body. This is pretty standard
in the Python world - a great way to show what your implementation does
and how somebody else can use it!
"""

# Problem 1
def isPalindrome(s):
  """Is s a palindrome?
  Args:
    s String to test
  Returns:
    True iff s is a palindrome. False otherwise.
  """
  return s == s[::-1]  # Super slicing :)

# Problem 1 Test Cases
# assert is a great way to make sure your code works properly
# If you try to assert a boolean false value, you will see an error!
# We'll go over this more in class!
assert isPalindrome("")
assert isPalindrome("9")
assert isPalindrome("racecar")
assert isPalindrome("not ton")
assert not isPalindrome("was it a rat i saw")
assert not isPalindrome("Malayalam")


# Problem 2
def isMultiple(i):
  """Returns True iff i is a multiple of both 3 and 4.
  Args:
    i Integer to test
  Returns:
    True iff i is a multiple of both 3 and 4. False otherwise.
  """
  return (i % 3 == 0) and (i % 4 == 0)

def sumOfMultiples(i):
  """Returns the sum of all numbers less than i that are multiples of
  both three and four.
  Args:
    i Integer the upper limit to sum
  Returns:
    Integer sum
  """
  return sum([n for n in range(i) if isMultiple(n)])

# Problem 2 Test Cases
assert isMultiple(0)
assert isMultiple(12)
assert isMultiple(24)
assert not isMultiple(13)
assert sumOfMultiples(0) == 0
assert sumOfMultiples(1) == 0
assert sumOfMultiples(13) == 12
assert sumOfMultiples(30) == 36


# Problem 3
def fib(n):
  """returns the nth fibonacci number
  Args:
    n Integer zero-based index of the fibonacci list
  Returns:
    Integer the nth fibonacci number
  """
  a = 1  # Temporary variables to hold last two fib numbers
  b = 1
  for temp in range(n):
    # We don't care about the value of temp.
    # We just want to loop n times
    (a, b) = (b, a+b)  # Tuple unpacking :)
  return b


def sumFib(n):
  """Returns the sum of the first n fibonacci numbers.
  Args:
    n Integer the number of fibs to sum up
  Returns:
    Integer sum
  """
  s = 0
  a = 1
  b = 1
  for temp in range(n):
    # Note that this solution doesn't use fib().
    # Why is this method more efficient?
    s += b
    (a, b) = (b, a+b)
  return s

# Problem 3 Test Cases
assert fib(0) == 1
assert fib(1) == 2
assert fib(2) == 3
assert fib(3) == 5
assert fib(4) == 8
assert sumFib(0) == 0
assert sumFib(1) == 1
assert sumFib(2) == 3
assert sumFib(3) == 6
assert sumFib(4) == 11