CS 1MD3 - Winter 2006 - Assignment #2

Generated for Student ID: 0571661

Due Date: Wednesday, February 8th

(You are responsible for verifying that your student number is correct!)

Part 1: Debugging

The following four functions are infested with bugs. Correct them by adding or changing a single line in each one. Clearly indicate your changes with comments. If you add a line, append the comment, "# added." If you change a line, append a comment to it containing the original, erroneous line. Solutions submitted without comments will not be marked.

1

def deinterlaceEven(interlacedList):
	"""Returns a list consisting of only the even elements of the given list.
	For example, deinterlaceEven(['1', 'a', '2', 'b', '3', 'c']) returns [1,2,3]."""
	n = len(interlacedList)
	if n == 0:
		return None
	i = 0
	evenList = []
	while i < n:
		evenList.append(interlacedList[i])
	i = i+2	
	return evenList

def hammingDistance(str1, str2):
	"""Returns the Hamming distance (or "edit distance") between two strings of the
	same length.  Hamming distance is defined as the minimum number of characters which
	must be changed	to make the strings identical.  For example, the Hamming distance
	between	"Python" and "Athlon" is 4 (only the last two letters are the same);
	the Hamming distance between "noodle" and "needle" is 2 (only the second and 
	third letters differ)."""
	if len(str1) != len(str2):
		return None
	list1 = list(str1)
	list2 = list(str2)
	n=len(list1)
	distance = 0
	i = 1-n
	while i <= 0:
		if list1[i] != list2[i]:
			distance = distance + 1
		i=i-1	
	return distance

def isPalindrome(aList):
	"""Returns True if the list reads the same backwards and forwards."""
	n = len(aList)
	cursor = 0
	while cursor < n:
		if (aList[cursor] != aList[-cursor]): 
			return False
		cursor=cursor+1
	return True

def reverseList(aList):
	"""Reverses the elements of a list.  Yes, yes... Python has a built-in function
	to do that, but what if someone steals it?  Ha!  Bet you never thought of that,
	did ya??"""
	n = len(aList)
	i = 0
	while i < n/2;	
		j = -i-1
		temp = aList[i]
		aList[i] = aList[j]
		aList[j] = temp
		i = i+1

Part 2: Testing

Create automated tests for the following function using PyUnit. Your tests should ensure that the code produces the expected result in all cases.

def gcd(intList):
	"""Finds the greatest common divisor among the list elements (in an inefficient way)."""
	if len(intList) == 0:
		return None
	isDivisor = False
	divider = 0
	listMin = min(intList)
	candidate = 1
	while isDivisor == False:
		divider = divider + 1
		if listMin != divider * (listMin / divider): # if divider isn't a factor of listMin...
			continue
		candidate = listMin / divider
		isDivisor = True
		for x in intList:
			if x != candidate * (x / candidate):
				isDivisor = False
				break
	return candidate