Week 9 Notes

# 

# Python Problem Solver

# Week 9 Example 1: Subbookkeeper 

#

N = int(input().strip())

line = input().strip()

newlist = []

answer = 0

for i in range(0,N):

    if line[i] == "?":

        if i == 0:

            newlist.append(line[i+1])

        else:

            newlist.append(line[i-1])

    else:

        newlist.append(line[i])

for i in range(0,N-1):

    if newlist[i] == newlist[i+1]:

        answer += 1

print(answer)

# 

# Python Problem Solver

# Week 9 Example 2: The Vigenere Cipher 1

#

original = input("Input the plain text: ").strip().upper()

key = int(input("Input the encryption key: ").strip())

cipher = ""

for c in original:

    asc = ord(c)

    asc += key

    if asc > 90:

        asc -= 26

    cipher += chr(asc)

print(f"The Caesar cipher of '{original}' is '{cipher}'.")

# 

# Python Problem Solver

# Week 9 Example 2: The Vigenere Cipher 2

#

original = input("Input the plain text: ").strip().upper()

key = input("Input the encryption key: ").strip().upper()

keylist = []

for k in key:

    keylist.append(ord(k) - 65)

keylist *= len(original)//len(key)+1

cipher = ""

for i in range(len(original)):

    asc = ord(original[i])

    asc += keylist[i]

    if asc > 90:

        asc -= 26

    cipher += chr(asc)

print(f"The Caesar cipher of '{original}' is '{cipher}'.")