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Simple implementation of basic algorithm.
The newest version!
/******************************************************************************
* Compilation: javac Alphabet.java
* Execution: java Alphabet
* Dependencies: StdOut.java
*
* A data type for alphabets, for use with string-processing code
* that must convert between an alphabet of size R and the integers
* 0 through R-1.
*
* Warning: supports only the basic multilingual plane (BMP), i.e,
* Unicode characters between U+0000 and U+FFFF.
*
******************************************************************************/
package edu.princeton.cs.algs4;
public class Alphabet {
/**
* The binary alphabet { 0, 1 }.
*/
public static final Alphabet BINARY = new Alphabet("01");
/**
* The octal alphabet { 0, 1, 2, 3, 4, 5, 6, 7 }.
*/
public static final Alphabet OCTAL = new Alphabet("01234567");
/**
* The decimal alphabet { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }.
*/
public static final Alphabet DECIMAL = new Alphabet("0123456789");
/**
* The hexadecimal alphabet { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F }.
*/
public static final Alphabet HEXADECIMAL = new Alphabet("0123456789ABCDEF");
/**
* The DNA alphabet { A, C, T, G }.
*/
public static final Alphabet DNA = new Alphabet("ACGT");
/**
* The lowercase alphabet { a, b, c, ..., z }.
*/
public static final Alphabet LOWERCASE = new Alphabet("abcdefghijklmnopqrstuvwxyz");
/**
* The uppercase alphabet { A, B, C, ..., Z }.
*/
public static final Alphabet UPPERCASE = new Alphabet("ABCDEFGHIJKLMNOPQRSTUVWXYZ");
/**
* The protein alphabet { A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, Y }.
*/
public static final Alphabet PROTEIN = new Alphabet("ACDEFGHIKLMNPQRSTVWY");
/**
* The base-64 alphabet (64 characters).
*/
public static final Alphabet BASE64 = new Alphabet("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
/**
* The ASCII alphabet (0-127).
*/
public static final Alphabet ASCII = new Alphabet(128);
/**
* The extended ASCII alphabet (0-255).
*/
public static final Alphabet EXTENDED_ASCII = new Alphabet(256);
/**
* The Unicode 16 alphabet (0-65,535).
*/
public static final Alphabet UNICODE16 = new Alphabet(65536);
private char[] alphabet; // the characters in the alphabet
private int[] inverse; // indices
private final int R; // the radix of the alphabet
/**
* Initializes a new alphabet from the given set of characters.
*
* @param alpha the set of characters
*/
public Alphabet(String alpha) {
// check that alphabet contains no duplicate chars
boolean[] unicode = new boolean[Character.MAX_VALUE];
for (int i = 0; i < alpha.length(); i++) {
char c = alpha.charAt(i);
if (unicode[c])
throw new IllegalArgumentException("Illegal alphabet: repeated character = '" + c + "'");
unicode[c] = true;
}
alphabet = alpha.toCharArray();
R = alpha.length();
inverse = new int[Character.MAX_VALUE];
for (int i = 0; i < inverse.length; i++)
inverse[i] = -1;
// can't use char since R can be as big as 65,536
for (int c = 0; c < R; c++)
inverse[alphabet[c]] = c;
}
/**
* Initializes a new alphabet using characters 0 through R-1.
*
* @param radix the number of characters in the alphabet (the radix R)
*/
private Alphabet(int radix) {
this.R = radix;
alphabet = new char[R];
inverse = new int[R];
// can't use char since R can be as big as 65,536
for (int i = 0; i < R; i++)
alphabet[i] = (char) i;
for (int i = 0; i < R; i++)
inverse[i] = i;
}
/**
* Initializes a new alphabet using characters 0 through 255.
*/
public Alphabet() {
this(256);
}
/**
* Returns true if the argument is a character in this alphabet.
*
* @param c the character
* @return {@code true} if {@code c} is a character in this alphabet;
* {@code false} otherwise
*/
public boolean contains(char c) {
return inverse[c] != -1;
}
/**
* Returns the number of characters in this alphabet (the radix).
*
* @return the number of characters in this alphabet
* @deprecated Replaced by {@link #radix()}.
*/
@Deprecated
public int R() {
return R;
}
/**
* Returns the number of characters in this alphabet (the radix).
*
* @return the number of characters in this alphabet
*/
public int radix() {
return R;
}
/**
* Returns the binary logarithm of the number of characters in this alphabet.
*
* @return the binary logarithm (rounded up) of the number of characters in this alphabet
*/
public int lgR() {
int lgR = 0;
for (int t = R-1; t >= 1; t /= 2)
lgR++;
return lgR;
}
/**
* Returns the index corresponding to the argument character.
*
* @param c the character
* @return the index corresponding to the character {@code c}
* @throws IllegalArgumentException unless {@code c} is a character in this alphabet
*/
public int toIndex(char c) {
if (c >= inverse.length || inverse[c] == -1) {
throw new IllegalArgumentException("Character " + c + " not in alphabet");
}
return inverse[c];
}
/**
* Returns the indices corresponding to the argument characters.
*
* @param s the characters
* @return the indices corresponding to the characters {@code s}
* @throws IllegalArgumentException unless every character in {@code s}
* is a character in this alphabet
*/
public int[] toIndices(String s) {
char[] source = s.toCharArray();
int[] target = new int[s.length()];
for (int i = 0; i < source.length; i++)
target[i] = toIndex(source[i]);
return target;
}
/**
* Returns the character corresponding to the argument index.
*
* @param index the index
* @return the character corresponding to the index {@code index}
* @throws IllegalArgumentException unless {@code 0 <= index < R}
*/
public char toChar(int index) {
if (index < 0 || index >= R) {
throw new IllegalArgumentException("index must be between 0 and " + R + ": " + index);
}
return alphabet[index];
}
/**
* Returns the characters corresponding to the argument indices.
*
* @param indices the indices
* @return the characters corresponding to the indices {@code indices}
* @throws IllegalArgumentException unless {@code 0 < indices[i] < R}
* for every {@code i}
*/
public String toChars(int[] indices) {
StringBuilder s = new StringBuilder(indices.length);
for (int i = 0; i < indices.length; i++)
s.append(toChar(indices[i]));
return s.toString();
}
/**
* Unit tests the {@code Alphabet} data type.
*
* @param args the command-line arguments
*/
public static void main(String[] args) {
int[] encoded1 = Alphabet.BASE64.toIndices("NowIsTheTimeForAllGoodMen");
String decoded1 = Alphabet.BASE64.toChars(encoded1);
StdOut.println(decoded1);
int[] encoded2 = Alphabet.DNA.toIndices("AACGAACGGTTTACCCCG");
String decoded2 = Alphabet.DNA.toChars(encoded2);
StdOut.println(decoded2);
int[] encoded3 = Alphabet.DECIMAL.toIndices("01234567890123456789");
String decoded3 = Alphabet.DECIMAL.toChars(encoded3);
StdOut.println(decoded3);
}
}
/******************************************************************************
* Copyright 2002-2018, Robert Sedgewick and Kevin Wayne.
*
* This file is part of algs4.jar, which accompanies the textbook
*
* Algorithms, 4th edition by Robert Sedgewick and Kevin Wayne,
* Addison-Wesley Professional, 2011, ISBN 0-321-57351-X.
* http://algs4.cs.princeton.edu
*
*
* algs4.jar is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* algs4.jar is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with algs4.jar. If not, see http://www.gnu.org/licenses.
******************************************************************************/
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