CS 101 Fall 25 Exam 2: Sec01 and Sec02

===================================================================
PROBLEM 1: SECTION 01
===================================================================

OUTPUT:
[0, 4, 5, 6, 7, 8, 9]

#----------------------------

OUTPUT:
[4, 5]

#----------------------------

OUTPUT:
[7, 8]
[0, 5, 6, 7, 8, 9]
[5, 6]

#----------------------------

OUTPUT:
['A', 'A', 'G', 'H']
[2, 6, 0]   # ANY ORDER
[0, 2, 5, 6]
['G', 'G', 'H', 'R']

===================================================================
PROBLEM 1: SECTION 02
===================================================================

OUTPUT:
[0, 1, 2, 3, 5, 6, 9]

#----------------------------

OUTPUT:
[3, 4, 5]

#----------------------------

OUTPUT:
[3, 7]
[1, 2, 3, 4, 6, 7]
[2, 6]

#----------------------------

OUTPUT:
['B', 'H', 'X', 'Z']
[2, 9]    # ANY ORDER
[2, 3, 4, 5, 9]
['B', 'H', 'T', 'V', 'X']

======================
PROBLEM 2 PART A
======================

result = [ word for word in lst if word.count(word[-1]) > 1 ]      # uses count on word
                               ... word[:-1].count(word[-1]) > 0 ] # uses count on substr

                               ... word[-1] in word[:-1] ]         # uses 'in'

                               ... word.find(word[-1]) < len(word)-1 ] # uses find on word
                               ... word[:-1].find(word[-1]) > -1 ]     # uses find on substr

                               ... word.index(word[-1]) < len(word)-1 ] # uses index on word (can't be substr!)
======================
PROBLEM 2 PART B
======================

result = [ 101+x for x in lst if str(x)[-1] == str(x)[-2] ] # uses str to get digits

OR 

result = [ 101+x for x in lst if x % 10 == (x//10) % 10 ] # solves for digits with mod

OR

result = [ 101+x for x in lst if (x % 100) % 11 == 0 ] # clever mod

======================
PROBLEM 2 PART C
======================

result = [ x[len(x)//2:] for x in lst if len(x)%2 == 0 ]

OR 

result = [ x[len(x)//2:] for x in lst if len(x)/2 == len(x)//2 ]

======================
PROBLEM 3 PART A
======================

result = []
for word in phrase.split():
	last = word[-1]
	first = word[0]
	new_word = word[:-1] + first + last
	result.append( (last, new_word) )

OR 

result = [ (word[-1], word[:-1] + word[0] + word[-1]) for word in phrase.split() ]

======================
PROBLEM 3 PART B
======================

maxMem = -1
for i in range(len(memory)):
	if prices[i] <= 1500 and memory[i] > maxMem:
		maxMem = memory[i]
result = maxMem # or use result directly in place of maxMem

OR 

result = max(memory[i] for i in range(len(memory)) if prices[i] <= 1500)

# OR a combination of these ideas (compute max in each iteration vs. use max() func at end)

======================
PROBLEM 3 PART C
======================

result = sorted(set(phrase2.split()) - set(phrase1.split()))

OR 

result = sorted(set(phrase2.split()).difference(set(phrase1.split())))

OR 

result = []

for word in phrase2.split():
	if word not in phrase1.split():
		result.append(word)

========================
PROBLEM 4 PART A
========================

maxMem = -1
def topFaves(datalist, movie):
	count = 0
	for row in datalist:
		if movie in row[3][:2]:
		# alternative: if movie == row[3][0] or movie == row[3][1]:
			count += 1

	return count

OR

def topFaves(datalist, movie):
	count = 0
	for _, _, _, faves in datalist:
		if movie in faves: # necessary, otherwise .index() raises exception!
			idx = faves.index(movie)
			if idx == 0 or idx == 1:
				count += 1
			
	return count

========================
PROBLEM 4 PART B
========================

def likelyFunds(datalist, chance):
	funds = []
	for row in datalist:
		if row[2] >= chance:
			funds.append(row[1])

	return sorted(funds)

OR

def likelyFunds(datalist, chance):
	funds = []
	for _, donation, prob, _ in datalist:
		if prob >= chance:
			funds.append(donation)

	return sorted(funds)

OR

def likelyFunds(datalist, chance):
	return sorted( [row[1] for row in datalist if row[2] >= chance] )

========================
PROBLEM 4 PART C
========================

def movieLovers(datalist):
	netids = []
	maxUniques = 0

	for i in range(len(datalist)):
		others = []

		# get movies favorited by anyone other than student i
		for j in range(len(datalist)):
			if i != j:
				others += datalist[j][3]
		
		uniques = set(row[i][3]) - set(others) # get unique movies for i
		if len(uniques) > maxUniques:		   # if more than seen previously, new max
			netids = [datalist[i][0]]		   # start new list with only this student
			maxUniques = len(uniques)		   # update maxUniques
		elif len(uniques) == maxUniques:       # student i matches current max; add to list
			netids.append(datalist[i][0])
			
	return sorted(netids)

def movieLovers(datalist):
	
	# start parallel lists
	netids = []
	maxUniques = 0

	for row in datalist:
		netid = row[0]
		uniques = set(row[3])

		# find movies not favorited by anyone else
		for movie in movies:

			for row2 in datalist:
				if row1 != row2 and movie in row2[3]:
					uniques.remove(movie)
		
		if len(uniques) > maxUniques:
			maxUniques = len(uniques)
			netids = []

		if len(uniques) == maxUniques:
			netids.append(netid)

	return sorted(netids)

def movieLovers(datalist):
	
	# start parallel lists
	netids = []
	numUniques = []

	for row in datalist:
		netid = row[0]
		movies = set(row[3])

		# remove movies favorited by someone else
		for movie in movies:
			for row2 in datalist:
				netid2 = row2[0]

				if netid != netid2:
					movies2 = set(row2[3])
					movies = movies - movies2

		# update parallel lists
		netids.append(netid)
		numUniques.append(len(movies))

	# return student netids with max number of uniques
	maxUnique = max(numUniques)
	return sorted( [ netids[i] for i in range(len(netids)) if numUniques[i] == maxUnique] )

OR

def movieLovers(datalist):
	# initialize list (to allow duplicates)
	movies = []

	# compute list of all movies
	for row in datalist:
		for movie in row[3]:
			favesWithRepeats += row[3]

	# initialize parallel lists
	netids = []
	numUniques = []

	# count number of movies favorited by exactly one student (must be the current one)
	for row in datalist:
		uniques = [ movie for movie in row[3] if favesWithRepeats.count(movie) == 1 ]
		numUniques.append(len(uniques))

	# return student netids with max number of uniques
	maxUniques = max(numUniques)
	return sorted(datalist[i][0] for i in range(len(datalist)) if numUniques[i] == maxUniques)

OR

def movieLovers(datalist):
	uniques = set()
	nonUniques = set()

	# compute set of movies uniquely favorited
	for row in datalist:
		for movie in row[3]:
			if movie not in nonUniques and movie not in uniques:
				uniques.add(movie)
			elif movie in uniques:
				uniques.remove(movie)
				nonuniques.add(movie)

	# count uniques per student
	numUniques = []
	for row in datalist:
		numUnique = 0
		for movie in row[3]:
			if movie in uniques:
				numUnique += 1

	# return student netids with max number of uniques
	maxUniques = max(numUniques)
	return sorted(datalist[i][0] for i in range(len(datalist)) if numUniques[i] == maxUniques)

==============================
PROBLEM 4 PART D
==============================

def favesThese(datalist, movies):
	netids = []
	for row in datalist:
		for movie in row[3]:
			if movie in movies:
				netids.append(row[0])

	return sorted(netids)

OR

def favesThese(datalist, movies):
	netids = []
	for row in datalist:
		if len(set(movies) & set(datalist[3])) > 0:
		# alternatively:
		# if set(movies) & set(datalist[3]):
			netids.append(row[0])

	return sorted(netids)

OR 

def favesThese(datalist, movies):
	return sorted(row[0] for row in datalist if set(row[3]) & set(movies) != set() )

==============================
PROBLEM 4 PART E
==============================

def processFile(filename):
	f = open(filename)
	datalist = [ ]
	for line in f:
		parts = line.split(':')
		left = parts[0].split('-')
		movies = left[-1] + parts # first movie is between last hyphen, first colon
		
		netid = left[0]
		donation = int(left[1])
		prob = float(left[2])

		datalist.append( [left[0], int(left[1]), float(left[2]), movies] )

	f.close()
	return datalist

OR 

def processFile(filename):
	f = open(filename)
	datalist = [ ]
	for line in f:
		parts = line.split('-') # assumes no hyphens in movie titles, OK
		movies = parts[-1].split(':')
		netid = parts[0]
		donation = int(parts[1])
		prob = float(parts[2])

		datalist.append( [netid, donation, prob, movies] )

	f.close()
	return datalist