caesar
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Tasks.md
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Tasks.md
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@ -282,8 +282,51 @@ Use [regex101.com](https://regex101.com) if you are not already a REGEX expert.
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There should be $374$ matches.
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There should be $374$ matches.
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A regex that fullfills the requirements is `\b[a-z][AEIOUaeiou]([a-w]|[A-W])`.
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A regex that matches the requirements is `\b[a-z][AEIOUaeiou]([a-w]|[A-W])`.
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[Code Example](src/tasks/regex.py)
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[Code Example](src/tasks/regex.py)
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</details>
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</details>
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## Ancient Cryptography
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Difficulty: 2/5
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<details>
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<summary>Text</summary>
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```text
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Neovim is a refactor, and sometimes redactor, in the tradition of Vim (which itself derives from
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Stevie). It is not a rewrite but a continuation and extension of Vim. Many clones and derivatives
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exist, some very clever—but none are Vim. Neovim is built for users who want the good parts of
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Vim, and more.
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````
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</details>
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1. The text above has been cyphered with the Caesar cipher, a timeless classic
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algorithm to abstract the meaning away from a text and arguably an early
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form of encryption. Your task is to decipher it back into readable text.
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### The caesar cipher
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For the caesar cipher, all letters are shifted by the value of the key.
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**Examples**
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"foo Bar" becomes "gpp Cbs" when shifted by $1$.
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<details>
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<summary>Hints</summary>
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</details>
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<details>
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<summary>Solution</summary>
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[Code Example](src/caesar.py)
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</details>
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@ -0,0 +1,46 @@
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#!/usr/bin/env python3
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import sys
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def internal(text: str, key: int) -> str:
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cyphertext: str = ""
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for c in text:
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if ord(c) >= 65 and ord(c) <= 90: # uppercase letters
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ci = ord(c) - ord('A')
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add = ord('A')
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#print(f"{c} is uppercase")
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elif ord(c) >= 97 and ord(c) <= 122: # uppercase letters
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ci = ord(c) - ord('a')
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add = ord('a')
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#print(f"{c} is lowercase")
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else:
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#print(f"not a letter: {c} ({ord(c)})")
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# character is not a letter, just skip it
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cyphertext += c
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continue
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ci += key
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ci %= 26 # only 23 letters in the alphabet
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#print(f"ci for {c}: {ci}")
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cyphertext += chr(ci + add)
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return cyphertext
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if len(sys.argv) <= 2 or len(sys.argv) >= 5:
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print("Takes two arguments: <SOURCE> <KEY> [-e]")
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exit(1)
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source: str = sys.argv[1]
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target: str = ""
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key = int(sys.argv[2])
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if len(sys.argv) >= 4 and sys.argv[3] == "-e":
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print("encrypting...")
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target = internal(source, -key)
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else:
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print("decrypting...")
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target = internal(source, key)
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print("=" * 80)
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print("%s" % target)
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