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p059.java
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p059.java
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/*
* Solution to Project Euler problem 59
* Copyright (c) Project Nayuki. All rights reserved.
*
* https://www.nayuki.io/page/project-euler-solutions
* https://github.com/nayuki/Project-Euler-solutions
*/
public final class p059 implements EulerSolution {
public static void main(String[] args) {
System.out.println(new p059().run());
}
public String run() {
byte[] bestKey = null;
byte[] bestDecrypted = null;
double bestScore = Double.NaN;
for (byte x = 'a'; x <= 'z'; x++) {
for (byte y = 'a'; y <= 'z'; y++) {
for (byte z = 'a'; z <= 'z'; z++) {
byte[] key = {x, y, z};
byte[] decrypted = decrypt(CIPHERTEXT, key);
double score = score(decrypted);
if (bestKey == null || score > bestScore) {
bestKey = key;
bestDecrypted = decrypted;
bestScore = score;
}
}
}
}
int sum = 0;
for (int i = 0; i < bestDecrypted.length; i++)
sum += bestDecrypted[i];
return Integer.toString(sum);
}
// Heuristical function that returns a penalty score, where lower is better.
// The current implementation returns only integral values, but floating-point values are legal too.
private static double score(byte[] b) {
double sum = 0;
for (int i = 0; i < b.length; i++) {
char c = (char)b[i];
if ('A' <= c && c <= 'Z')
sum += 1; // Uppercase letters are good
else if ('a' <= c && c <= 'z')
sum += 2; // Lowercase letters are excellent
else if (c < 0x20 || c == 0x7F)
sum -= 10; // Control characters are very bad
}
return sum;
}
private static byte[] decrypt(byte[] ciphertext, byte[] key) {
byte[] plaintext = new byte[ciphertext.length];
for (int i = 0; i < ciphertext.length; i++)
plaintext[i] = (byte)(ciphertext[i] ^ key[i % key.length]);
return plaintext;
}
private static final byte[] CIPHERTEXT = {
36, 22, 80, 0, 0, 4, 23, 25, 19, 17, 88, 4, 4, 19, 21, 11, 88, 22, 23, 23,
29, 69, 12, 24, 0, 88, 25, 11, 12, 2, 10, 28, 5, 6, 12, 25, 10, 22, 80, 10,
30, 80, 10, 22, 21, 69, 23, 22, 69, 61, 5, 9, 29, 2, 66, 11, 80, 8, 23, 3,
17, 88, 19, 0, 20, 21, 7, 10, 17, 17, 29, 20, 69, 8, 17, 21, 29, 2, 22, 84,
80, 71, 60, 21, 69, 11, 5, 8, 21, 25, 22, 88, 3, 0, 10, 25, 0, 10, 5, 8,
88, 2, 0, 27, 25, 21, 10, 31, 6, 25, 2, 16, 21, 82, 69, 35, 63, 11, 88, 4,
13, 29, 80, 22, 13, 29, 22, 88, 31, 3, 88, 3, 0, 10, 25, 0, 11, 80, 10, 30,
80, 23, 29, 19, 12, 8, 2, 10, 27, 17, 9, 11, 45, 95, 88, 57, 69, 16, 17, 19,
29, 80, 23, 29, 19, 0, 22, 4, 9, 1, 80, 3, 23, 5, 11, 28, 92, 69, 9, 5,
12, 12, 21, 69, 13, 30, 0, 0, 0, 0, 27, 4, 0, 28, 28, 28, 84, 80, 4, 22,
80, 0, 20, 21, 2, 25, 30, 17, 88, 21, 29, 8, 2, 0, 11, 3, 12, 23, 30, 69,
30, 31, 23, 88, 4, 13, 29, 80, 0, 22, 4, 12, 10, 21, 69, 11, 5, 8, 88, 31,
3, 88, 4, 13, 17, 3, 69, 11, 21, 23, 17, 21, 22, 88, 65, 69, 83, 80, 84, 87,
68, 69, 83, 80, 84, 87, 73, 69, 83, 80, 84, 87, 65, 83, 88, 91, 69, 29, 4, 6,
86, 92, 69, 15, 24, 12, 27, 24, 69, 28, 21, 21, 29, 30, 1, 11, 80, 10, 22, 80,
17, 16, 21, 69, 9, 5, 4, 28, 2, 4, 12, 5, 23, 29, 80, 10, 30, 80, 17, 16,
21, 69, 27, 25, 23, 27, 28, 0, 84, 80, 22, 23, 80, 17, 16, 17, 17, 88, 25, 3,
88, 4, 13, 29, 80, 17, 10, 5, 0, 88, 3, 16, 21, 80, 10, 30, 80, 17, 16, 25,
22, 88, 3, 0, 10, 25, 0, 11, 80, 12, 11, 80, 10, 26, 4, 4, 17, 30, 0, 28,
92, 69, 30, 2, 10, 21, 80, 12, 12, 80, 4, 12, 80, 10, 22, 19, 0, 88, 4, 13,
29, 80, 20, 13, 17, 1, 10, 17, 17, 13, 2, 0, 88, 31, 3, 88, 4, 13, 29, 80,
6, 17, 2, 6, 20, 21, 69, 30, 31, 9, 20, 31, 18, 11, 94, 69, 54, 17, 8, 29,
28, 28, 84, 80, 44, 88, 24, 4, 14, 21, 69, 30, 31, 16, 22, 20, 69, 12, 24, 4,
12, 80, 17, 16, 21, 69, 11, 5, 8, 88, 31, 3, 88, 4, 13, 17, 3, 69, 11, 21,
23, 17, 21, 22, 88, 25, 22, 88, 17, 69, 11, 25, 29, 12, 24, 69, 8, 17, 23, 12,
80, 10, 30, 80, 17, 16, 21, 69, 11, 1, 16, 25, 2, 0, 88, 31, 3, 88, 4, 13,
29, 80, 21, 29, 2, 12, 21, 21, 17, 29, 2, 69, 23, 22, 69, 12, 24, 0, 88, 19,
12, 10, 19, 9, 29, 80, 18, 16, 31, 22, 29, 80, 1, 17, 17, 8, 29, 4, 0, 10,
80, 12, 11, 80, 84, 67, 80, 10, 10, 80, 7, 1, 80, 21, 13, 4, 17, 17, 30, 2,
88, 4, 13, 29, 80, 22, 13, 29, 69, 23, 22, 69, 12, 24, 12, 11, 80, 22, 29, 2,
12, 29, 3, 69, 29, 1, 16, 25, 28, 69, 12, 31, 69, 11, 92, 69, 17, 4, 69, 16,
17, 22, 88, 4, 13, 29, 80, 23, 25, 4, 12, 23, 80, 22, 9, 2, 17, 80, 70, 76,
88, 29, 16, 20, 4, 12, 8, 28, 12, 29, 20, 69, 26, 9, 69, 11, 80, 17, 23, 80,
84, 88, 31, 3, 88, 4, 13, 29, 80, 21, 29, 2, 12, 21, 21, 17, 29, 2, 69, 12,
31, 69, 12, 24, 0, 88, 20, 12, 25, 29, 0, 12, 21, 23, 86, 80, 44, 88, 7, 12,
20, 28, 69, 11, 31, 10, 22, 80, 22, 16, 31, 18, 88, 4, 13, 25, 4, 69, 12, 24,
0, 88, 3, 16, 21, 80, 10, 30, 80, 17, 16, 25, 22, 88, 3, 0, 10, 25, 0, 11,
80, 17, 23, 80, 7, 29, 80, 4, 8, 0, 23, 23, 8, 12, 21, 17, 17, 29, 28, 28,
88, 65, 75, 78, 68, 81, 65, 67, 81, 72, 70, 83, 64, 68, 87, 74, 70, 81, 75, 70,
81, 67, 80, 4, 22, 20, 69, 30, 2, 10, 21, 80, 8, 13, 28, 17, 17, 0, 9, 1,
25, 11, 31, 80, 17, 16, 25, 22, 88, 30, 16, 21, 18, 0, 10, 80, 7, 1, 80, 22,
17, 8, 73, 88, 17, 11, 28, 80, 17, 16, 21, 11, 88, 4, 4, 19, 25, 11, 31, 80,
17, 16, 21, 69, 11, 1, 16, 25, 2, 0, 88, 2, 10, 23, 4, 73, 88, 4, 13, 29,
80, 11, 13, 29, 7, 29, 2, 69, 75, 94, 84, 76, 65, 80, 65, 66, 83, 77, 67, 80,
64, 73, 82, 65, 67, 87, 75, 72, 69, 17, 3, 69, 17, 30, 1, 29, 21, 1, 88, 0,
23, 23, 20, 16, 27, 21, 1, 84, 80, 18, 16, 25, 6, 16, 80, 0, 0, 0, 23, 29,
3, 22, 29, 3, 69, 12, 24, 0, 88, 0, 0, 10, 25, 8, 29, 4, 0, 10, 80, 10,
30, 80, 4, 88, 19, 12, 10, 19, 9, 29, 80, 18, 16, 31, 22, 29, 80, 1, 17, 17,
8, 29, 4, 0, 10, 80, 12, 11, 80, 84, 86, 80, 35, 23, 28, 9, 23, 7, 12, 22,
23, 69, 25, 23, 4, 17, 30, 69, 12, 24, 0, 88, 3, 4, 21, 21, 69, 11, 4, 0,
8, 3, 69, 26, 9, 69, 15, 24, 12, 27, 24, 69, 49, 80, 13, 25, 20, 69, 25, 2,
23, 17, 6, 0, 28, 80, 4, 12, 80, 17, 16, 25, 22, 88, 3, 16, 21, 92, 69, 49,
80, 13, 25, 6, 0, 88, 20, 12, 11, 19, 10, 14, 21, 23, 29, 20, 69, 12, 24, 4,
12, 80, 17, 16, 21, 69, 11, 5, 8, 88, 31, 3, 88, 4, 13, 29, 80, 22, 29, 2,
12, 29, 3, 69, 73, 80, 78, 88, 65, 74, 73, 70, 69, 83, 80, 84, 87, 72, 84, 88,
91, 69, 73, 95, 87, 77, 70, 69, 83, 80, 84, 87, 70, 87, 77, 80, 78, 88, 21, 17,
27, 94, 69, 25, 28, 22, 23, 80, 1, 29, 0, 0, 22, 20, 22, 88, 31, 11, 88, 4,
13, 29, 80, 20, 13, 17, 1, 10, 17, 17, 13, 2, 0, 88, 31, 3, 88, 4, 13, 29,
80, 6, 17, 2, 6, 20, 21, 75, 88, 62, 4, 21, 21, 9, 1, 92, 69, 12, 24, 0,
88, 3, 16, 21, 80, 10, 30, 80, 17, 16, 25, 22, 88, 29, 16, 20, 4, 12, 8, 28,
12, 29, 20, 69, 26, 9, 69, 65, 64, 69, 31, 25, 19, 29, 3, 69, 12, 24, 0, 88,
18, 12, 9, 5, 4, 28, 2, 4, 12, 21, 69, 80, 22, 10, 13, 2, 17, 16, 80, 21,
23, 7, 0, 10, 89, 69, 23, 22, 69, 12, 24, 0, 88, 19, 12, 10, 19, 16, 21, 22,
0, 10, 21, 11, 27, 21, 69, 23, 22, 69, 12, 24, 0, 88, 0, 0, 10, 25, 8, 29,
4, 0, 10, 80, 10, 30, 80, 4, 88, 19, 12, 10, 19, 9, 29, 80, 18, 16, 31, 22,
29, 80, 1, 17, 17, 8, 29, 4, 0, 10, 80, 12, 11, 80, 84, 86, 80, 36, 22, 20,
69, 26, 9, 69, 11, 25, 8, 17, 28, 4, 10, 80, 23, 29, 17, 22, 23, 30, 12, 22,
23, 69, 49, 80, 13, 25, 6, 0, 88, 28, 12, 19, 21, 18, 17, 3, 0, 88, 18, 0,
29, 30, 69, 25, 18, 9, 29, 80, 17, 23, 80, 1, 29, 4, 0, 10, 29, 12, 22, 21,
69, 12, 24, 0, 88, 3, 16, 21, 3, 69, 23, 22, 69, 12, 24, 0, 88, 3, 16, 26,
3, 0, 9, 5, 0, 22, 4, 69, 11, 21, 23, 17, 21, 22, 88, 25, 11, 88, 7, 13,
17, 19, 13, 88, 4, 13, 29, 80, 0, 0, 0, 10, 22, 21, 11, 12, 3, 69, 25, 2,
0, 88, 21, 19, 29, 30, 69, 22, 5, 8, 26, 21, 23, 11, 94,
};
}