CMU Coding Bootcamp
thecoded.prof
1def encodeSimpleCipher(s: str) -> str:
2 """
3 Encode a string using this formula.
4 - s[i] = 2*i
5 - if 2*i > len(s), s[i] = (2*i) % len(s)
6 """
7 encoded = list(s)
8 for i in range(len(s)):
9 j = (2 * i) % len(s)
10 cj = encoded[j]
11 encoded[j] = encoded[i]
12 encoded[i] = cj
13 return "".join(encoded)
14
15
16def decodeSimpleCipher(s: str) -> str:
17 """Decode a string encoded from encodeSimpleCipher"""
18 decoded = list(s)
19 for i in range(len(s) - 1, -1, -1):
20 j = (2 * i) % len(s)
21 cj = decoded[j]
22 decoded[j] = decoded[i]
23 decoded[i] = cj
24 return "".join(decoded)
25
26
27print("Testing encodeSimpleCipher()...", end="")
28assert encodeSimpleCipher("AB") == "BA"
29assert encodeSimpleCipher("ABC") == "ABC"
30assert encodeSimpleCipher("ABCD") == "BCDA"
31assert encodeSimpleCipher("ABCDEFGH") == "BCFGDEHA"
32assert encodeSimpleCipher("SECRET MESSAGE") == "MCE SSTSAEREEG"
33assert (
34 encodeSimpleCipher("THIS IS A LONGER SECRET MESSAGE JUST FOR YOU!")
35 == "T SAENG SR MGARJ H U!SSTE TFECORIIEYSELUOOS"
36)
37print("Passed!")
38
39
40print("Testing decodeSimpleCipher()...", end="")
41assert decodeSimpleCipher("BA") == "AB"
42assert decodeSimpleCipher("ABC") == "ABC"
43assert decodeSimpleCipher("BCDA") == "ABCD"
44assert decodeSimpleCipher("BCFGDEHA") == "ABCDEFGH"
45assert decodeSimpleCipher("MCE SSTSAEREEG") == "SECRET MESSAGE"
46assert (
47 decodeSimpleCipher("T SAENG SR MGARJ H U!SSTE TFECORIIEYSELUOOS")
48 == "THIS IS A LONGER SECRET MESSAGE JUST FOR YOU!"
49)
50print("Passed!")