-
Notifications
You must be signed in to change notification settings - Fork 0
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
- Loading branch information
1 parent
29a1ed8
commit 53ec2e0
Showing
8 changed files
with
57 additions
and
2 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,46 @@ | ||
/* | ||
Project Euler Problem 59 | ||
Problem: | ||
Each character on a computer is assigned a unique code and the preferred | ||
standard is ASCII (American Standard Code for Information Interchange). For | ||
example, uppercase A = 65, asterisk (*) = 42, and lowercase k = 107. | ||
A modern encryption method is to take a text file, convert the bytes to ASCII, | ||
then XOR each byte with a given value, taken from a secret key. The advantage | ||
with the XOR function is that using the same encryption key on the cipher text, | ||
restores the plain text; for example, 65 XOR 42 = 107, then 107 XOR 42 = 65. | ||
For unbreakable encryption, the key is the same length as the plain text | ||
message, and the key is made up of random bytes. The user would keep the | ||
encrypted message and the encryption key in different locations, and without | ||
both "halves", it is impossible to decrypt the message. | ||
Unfortunately, this method is impractical for most users, so the modified | ||
method is to use a password as a key. If the password is shorter than the | ||
message, which is likely, the key is repeated cyclically throughout the | ||
message. The balance for this method is using a sufficiently long password key | ||
for security, but short enough to be memorable. | ||
Your task has been made easy, as the encryption key consists of three lower | ||
case characters. Using cipher.txt (right click and 'Save Link/Target As...'), | ||
a file containing the encrypted ASCII codes, and the knowledge that the plain | ||
text must contain common English words, decrypt the message and find the sum of | ||
the ASCII values in the original text. | ||
*/ | ||
use itertools::Itertools; | ||
|
||
use crate::include::utils::{get_data_file,Answer}; | ||
|
||
pub fn p0059() -> Answer { | ||
let keyword = b"beginning"; | ||
let tokens = get_data_file("p0059_cipher.txt").split(',').map(|x| x.parse::<u8>().unwrap()).collect::<Vec<u8>>(); | ||
for key in b"abcdefghijklmnopqrtsuvwxyz".into_iter().permutations(3) { | ||
let plaintext = tokens.iter().enumerate().map(|(i, x)| *x ^ key[i % 3]).collect::<Vec<u8>>(); | ||
if plaintext.windows(keyword.len()).any(|w| w == keyword) { | ||
return Answer::Int(plaintext.into_iter().sum::<u64>().into()); | ||
} | ||
} | ||
return Answer::Int(-1); | ||
} |