CS101 Final Exam

國立暨南國際大學 105 學年度第一學期期末考試卷

科目名稱：計算機概論		開課系所：資訊工程學系		考試日期	2017.1.4
系所別：	年級：	學號：	姓名：	考試時間	08:20-10:00

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(10%) Determine whether the following code has syntax errors or not. If it is correct, predict its output. If it is incorrect, point out the mistake(s).

# String Methods (P.142)
def main():
    plaintext = "FCPPXOCYYECP"
    t = ['ABCDE', 'FGHIJ', 'KLMNO', 'PQRST', 'UVWXY']
    ciphertext = enc(plaintext, t)
    print(ciphertext)

def enc(s, tabula):
    ciphertext = ""
    for i in range(0, len(s)-1, 2):
        x1, y1, x2, y2 = findDiagonal(tabula, s[i:i+2])
        c3c4 = getDiagonal(tabula, x1, y2, x2, y1)
        ciphertext = ciphertext + c3c4
    return ciphertext

def getDiagonal(tabula, x1, y1, x2, y2):
    return tabula[x1][y1] + tabula[x2][y2]

def findDiagonal(tabula, s):
    # s is a 2-character string
    c1, c2 = s[0], s[1]
    longStr = "".join(tabula)
    p1 = longStr.find(c1)
    x1, y1 = p1 // 5, p1 % 5
    p2 = longStr.find(c2)
    x2, y2 = p2 // 5, p2 % 5
    return x1, y1, x2, y2

if __name__ == "__main__":
    main()
(10%) Determine whether the following code has syntax errors or not. If it is correct, predict its output. If it is incorrect, point out the mistake(s).

# Recursive Functions (P.468)
def anagrams(s):
    if s == "":
        return [s]
    else:
        ans = []
        for w in anagrams(s[1:]):
            for pos in range(len(w)+1):
                ans.append(w[:pos]+s[0]+w[pos:])
        return ans

print( anagrams("book") )
(10%) Determine whether the following code has syntax errors or not. If it is correct, predict its output. If it is incorrect, point out the mistake(s).

# Merge Sort (P.479)
def showList(nums):
    for x in nums:
        if x == nums[-1]:
            print(x, end='\n')
        else:
            print(x, end='\t')

def merge(lst1, lst2, lst3):
    i1, i2, i3 = 0, 0, 0 # all start at the front
    n1, n2 = len(lst1), len(lst2)

    while i1 < n1 and i2 < n2:
        if lst1[i1] < lst2[i2]: # top of lst1 is smaller
            lst3[i3] = lst1[i1] # copy it into current spot in lst3
            i1 = i1 + 1
        else:                   # top of lst2 is smaller
            lst3[i3] = lst2[i2] # copy itinto current spot in lst3
            i2 = i2 + 1
        i3 = i3 + 1             # item added to lst3, update position

    while i1 < n1:
        lst3[i3] = lst1[i1]
        i1 = i1 + 1
        i3 = i3 + 1

    while i2 < n2:
        lst3[i3] = lst2[i2]
        i2 = i2 + 1
        i3 = i3 + 1

def mergeSort(nums):
    n = len(nums)
    if n > 1:
        m = n//2
        nums1, nums2 = nums[:m], nums[m:]
        mergeSort(nums1)
        mergeSort(nums2)
        merge(nums1, nums2, nums)
        showList(nums)

a = [82, 45, 30, 48, 61, 77, 2, 14, 98, 57]
mergeSort(a)
(10%) Determine whether the following code has syntax errors or not. If it is correct, predict its output. If it is incorrect, point out the mistake(s).

# Nested loop (P.254) and break (P.263)
sum = 0
i = 1
while i < 5:
    j = i
    while j < 6:
        sum = sum + j
        if i < j: break
        j = j + 1
    i = i + 1
print(sum)
(10%) Determine whether the following code has syntax errors or not. If it is correct, predict its output. If it is incorrect, point out the mistake(s).

# String Formatting (P.154)
N = 5
s = " "*N + "{0}"
for i in range(N):
print( s[N-i:].format( "*"*(2*(N-i)-1) ) )
(10%) Determine whether the following code has syntax errors or not. If it is correct, predict its output. If it is incorrect, point out the mistake(s).

# List slicing and concatenation (P.367)
s1 = [1,2,3,4]
s2=['a','b','c','d']
print(s1[:2] + s2[-1:])
(10%) Determine whether the following code has syntax errors or not. If it is correct, predict its output. If it is incorrect, point out the mistake(s).

# File I/O (P.158)
def generate_data_file():
    ex7_data = """klim:10 20 30\nmilk:199
oak:100\nred:200 10
joe:198 22\nmarry:20\njulie:2000"""
    outfile = open("ex7.dat", "w")
    print(ex7_data, file=outfile)
    outfile.close()

def main():
    generate_data_file()
    infile = open("ex7.dat", "r")
    for line in infile:
        name, numbers = line.split(':')
        sum = 0
        numbers = numbers.split()
        for num in numbers:
            sum = sum + eval(num)
        print(name, int(sum / len(numbers)), sep=':' )
    infile.close()

if __name__ == "__main__":
    main()
(10%) Determine whether the following code has syntax errors or not. If it is correct, predict its output. If it is incorrect, point out the mistake(s).
# Define a class for Polynomial (P.321)
class Polynomial:
    def __init__(self, aList):
        self.coefficients = aList
    def __str__(self):
        def needPlus(coefficient, order):
            if order == 0:
                necessity = False
            else:
                if coefficient > 0:
                    necessity = True
                else:
                    necessity = False
            return necessity

        result = ""
        cList = self.coefficients
        for i in range( len(cList) ):
            a = cList[i]        # coefficient

            if i == 0:
                expo = ''
            elif i == 1:
                expo = 'x'
            else:
                expo = "x**" + str(i)

            if a != 0:
                if needPlus(a, i):
                    if a == 1:   # i must be gt 0, because needPlus
                        result = result + "+" + expo
                    else:
                        result = result + "+" + str( a ) + expo
                else:
                    if a == -1 and i > 0:
                        result = result + '-' + expo
                    else:
                        result = result + str(a) + expo
        return result

p1 = Polynomial([0, 0, 7])
p2 = Polynomial([0, 1, 0])
print(p1)
print(p2)
(10%) Determine whether the following code has syntax errors or not. If it is correct, predict its output. If it is incorrect, point out the mistake(s).

# Dictionary (P.401)
def generate_data_file():
    ex9_data = """klim 10 20 milk 199 joe 20
oak 100 red 200 10 klim 30
joe 199 marry 20 julie 2000"""
    outfile = open("ex9.dat", "w")
    print(ex9_data, file=outfile)
    outfile.close()

def main():
    generate_data_file()
    infile = open("ex9.dat", "r")
    count = {} # Dictionary
    sum = {}
    for line in infile:
        for item in line.split():
            if item.isalpha():
                name = item
            else:
                if not name in count:
                    count[name] = sum[name] = 0
                count[name] = count[name] + 1
                sum[name] = sum[name] + eval(item)
    infile.close()
    for k in sorted(count.keys()):
        print(k, count[k], sum[k])

if __name__ == "__main__":
    main()
(10%) Determine whether the following code has syntax errors or not. If it is correct, predict its output. If it is incorrect, point out the mistake(s).

# Key Function for Sorting (P.377)
class Student:
    def __init__(self, i, n, s):
        self.id, self.name, self.score = i, n, s
    def __str__(self):
        return str(self.id) + ' ' + self.name + ' ' + str(self.score)

def score(aStudent):
    return 100 - aStudent.score

students = [Student(580, "Alice",   35),
            Student(191, "Bob",     75),
            Student(641, "Charlie", 76),
            Student(813, "Dennis", 27),
            Student(809, "Emily",   79),
            Student(568, "Fiona",   65) ]
students.sort(key=score)
print( students[1] )

國立暨南國際大學 105 學年度第一學期 期末考試卷

國立暨南國際大學 105 學年度第一學期期末考試卷