Package net.n1da.dev.euler

Class PE0059

java.lang.Object

net.n1da.dev.euler.core.Problem

net.n1da.dev.euler.PE0059

All Implemented Interfaces:

Solvable

public class PE0059
extends Problem

Solution for problem 59 "XOR decryption" completed on Fri, 16 Dec 2016, 07:28.

Since:

10.12.2016 08:10:12

Author:

Nico Danneberg

See Also:

Problem @ Project Euler, Solution @ Ni-Da-Net

Field Summary

Fields

Modifier and Type	Field	Description
private byte[]	code	A memory for the code
private static double[]	StandardDistribution	Stores the standard distribution of letters in the English language

Fields inherited from class net.n1da.dev.euler.core.Problem

number, title

Constructor Summary

Constructors

Constructor	Description
PE0059()	A simple constructor to set number and title.

Method Summary

Modifier and Type	Method	Description
private byte[]	decode(byte[] code, byte[] key)	Decodes a given code by the given key using a bitwise XOR operation.
private double[]	getLetterDist(byte[] text)	Calculates the distribution of all letters in the given text.
void	prepare()	Prepares the problem by reading the code from a given file.
java.lang.String	solve()	All possible keys from [aaa] to [zzz] are generated.

Methods inherited from class net.n1da.dev.euler.core.Problem

finish, getResult, getRuntime, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

StandardDistribution

private static double[] StandardDistribution

Stores the standard distribution of letters in the English language

code

private byte[] code

A memory for the code

Constructor Detail

PE0059

public PE0059()

A simple constructor to set number and title.

Method Detail

prepare

public void prepare()

Prepares the problem by reading the code from a given file.

Specified by:

prepare in interface Solvable

Overrides:

prepare in class Problem

solve

public java.lang.String solve()

All possible keys from [aaa] to [zzz] are generated. The code is decoded by every key and the distribution of letters is calculated for every of these decoded texts. The text with the smallest deviation is the solution.

Returns:

the sum of the ASCII codes of all letters in the decoded text

decode

private byte[] decode(byte[] code,
                      byte[] key)

Decodes a given code by the given key using a bitwise XOR operation.

Parameters:

code - the code as array of bytes

key - the key as array of bytes

Returns:

the decoded text as the result of decoding

getLetterDist

private double[] getLetterDist(byte[] text)

Calculates the distribution of all letters in the given text. Both, lower and upper case versions of a letter, are counted as one.

Parameters:

text - the text to read the letters from

Returns:

an 26 elements big array with the relative count of each letter