ue6
This commit is contained in:
123
uebung06/src/sudoku/Field.java
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123
uebung06/src/sudoku/Field.java
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package sudoku;
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import java.util.ArrayList;
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import java.util.EnumSet;
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import java.util.List;
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import java.util.Set;
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import static java.util.Collections.emptySet;
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/**
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* A field of a Sudoku board.
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*/
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public class Field {
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private static final int DEP_LENGTH = 2 * Sudoku.SIZE + 2;
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public final Sudoku sudoku;
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public final int x;
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public final int y;
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private Value value;
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private List<Field> dependents;
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private final Set<Value> domain = EnumSet.allOf(Value.class);
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/**
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* Creates a field of the specified Sudoku board at the specified coordinates.
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*
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* @param sudoku the Sudoku board
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* @param x x coordinate (0 <= x < 9)
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* @param y y coordinate (0 <= y < 9)
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*/
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public Field(Sudoku sudoku, int x, int y) {
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if (x < 0 || x >= Sudoku.SIZE || y < 0 || y >= Sudoku.SIZE)
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throw new IllegalArgumentException("Illegal coordinates " + x + ", " + y);
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this.sudoku = sudoku;
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this.x = x;
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this.y = y;
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}
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/**
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* Returns the value of this field, or null if it is empty.
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*
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* @return the value of this field, or null if it is empty.
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*/
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public Value getValue() {
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return value;
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}
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/**
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* Sets the value of this field
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*
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* @param v the value, or null if this field shall be empty.
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*/
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public void setValue(Value v) {
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value = v;
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}
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/**
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* Removes the value of this field so that it is empty.
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*/
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public void clearValue() {
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setValue(null);
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}
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/**
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* Checks whether this field is empty.
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*
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* @return true iff this field is empty.
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*/
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public boolean isEmpty() {
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return value == null;
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}
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/**
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* Returns a string representation of this field. As a matter of fact,
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* its value is returned, or "." if it is empty.
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*
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* @return a string representation of this field.
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*/
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public String toString() {
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return isEmpty() ? "." : value.toString();
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}
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/**
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* Returns the set of all values possible for this field that do not violate the Sudoku constraints,
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* if the field is empty. Otherwise, it returns the empty set. The returned set may be modified if
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* the field is empty.
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*
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* @return the domain of this field.
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*/
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public Set<Value> getDomain() {
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return isEmpty() ? domain : emptySet();
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}
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/**
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* Returns the list of all other fields of this Sudoku field whose values are constrained by the
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* value of this field.
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*
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* @return the list of all dependent fields.
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*/
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List<Field> getDependents() {
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if (dependents == null) {
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dependents = new ArrayList<>(DEP_LENGTH);
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// fill the list with all fields in the given row and column
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for (int i = 0; i < Sudoku.SIZE; i++) {
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if (i != x)
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dependents.add(sudoku.field(i, y));
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if (i != y)
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dependents.add(sudoku.field(x, i));
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}
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// determine the coordinates of the upper left corner of this field's block
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final int x0 = 3 * (x / 3);
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final int y0 = 3 * (y / 3);
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// fill the list with the whole block
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for (int x1 = x0; x1 < x0 + 3; x1++)
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if (x1 != x)
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for (int y1 = y0; y1 < y0 + 3; y1++)
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if (y1 != y)
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dependents.add(sudoku.field(x1, y1));
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}
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return dependents;
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}
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}
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206
uebung06/src/sudoku/Sudoku.java
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206
uebung06/src/sudoku/Sudoku.java
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package sudoku;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* A Sudoku board as a matrix of {@linkplain sudoku.Field} instances.
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* <p>
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* Call {@linkplain #solve()} to solve it.
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*/
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public class Sudoku {
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/**
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* Edge size of the Sudoku board.
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*/
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public static final int SIZE = 9;
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private static final String LS = System.lineSeparator();
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private final Field[] board = new Field[SIZE * SIZE];
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/**
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* Creates a Sudoku board with all of its fields being empty.
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*/
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public Sudoku() {
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for (int x = 0; x < SIZE; x++)
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for (int y = 0; y < SIZE; y++)
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board[SIZE * y + x] = new Field(this, x, y);
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}
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/**
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* Returns the field at the specified coordinates
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*
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* @param x x coordinate (0 <= x < 9)
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* @param y y coordinate (0 <= x < 9)
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* @return the field at the specified coordinates
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*/
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public Field field(int x, int y) {
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return board[SIZE * y + x];
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}
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/**
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* Bulk operation to set values of the fields.
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*
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* @param values a sequence of integers where 0 means empty
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*/
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public void initialize(int... values) {
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if (values.length != board.length)
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throw new IllegalArgumentException("Wrong Sudoku board with " + values.length + " values");
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for (int i = 0; i < values.length; i++)
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if (values[i] != 0)
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setValue(board[i], Value.of(values[i]));
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}
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/**
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* Sets the specified value of the specified empty field
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*
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* @param field the empty field whose value is set
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* @param value the value of the field
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* @throws IllegalStateException if the field is not empty
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* @throws IllegalArgumentException if setting this value would violate the Sudoku constraints
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* @throws NullPointerException if the value is null
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*/
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public void setValue(Field field, Value value) {
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if (value == null)
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throw new NullPointerException("value is null");
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if (!field.isEmpty())
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throw new IllegalStateException("Value already set: " + field);
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if (!field.getDomain().contains(value))
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throw new IllegalArgumentException(value + " is not permitted");
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for (Field dependent : field.getDependents())
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dependent.getDomain().remove(value);
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field.setValue(value);
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}
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/**
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* Returns a string representation of this board.
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*
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* @return a string representation of this board
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*/
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public String toString() {
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StringBuilder sb = new StringBuilder();
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for (int y = 0; y < SIZE; y++) {
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if (y == 3 || y == 6) sb.append("---------+---------+---------").append(LS);
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for (int x = 0; x < SIZE; x++) {
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if (x == 3 || x == 6) sb.append("|");
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sb.append(" ").append(field(x, y)).append(" ");
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}
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sb.append(LS);
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}
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return sb.toString();
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}
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/**
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* Looks for an empty field with minimal domain.
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*
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* @return a field with minimal domain, or null no field is empty
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*/
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private Field findBestCandidate() {
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Field best = null;
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int min = Integer.MAX_VALUE;
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for (Field f : board)
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if (f.isEmpty() && f.getDomain().size() < min) {
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best = f;
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min = best.getDomain().size();
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}
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return best;
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}
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/**
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* Tries to solve the current board. The board is in the solved state if a solution is found,
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* and unmodified if no solution is found.
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*
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* @return true iff a solution has been found.
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*/
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public boolean solve() {
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final Field field = findBestCandidate();
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if (field == null)
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// A solution has been found
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return true;
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// There are empty fields. Try all values of its domain
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final List<Field> revoke = new ArrayList<>();
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for (Value v : field.getDomain()) {
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field.setValue(v);
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boolean consistent = true;
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for (Field dependent : field.getDependents())
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if (dependent.getDomain().contains(v)) {
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if (dependent.getDomain().size() == 1) {
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// This is a dead end because field 'dependent'
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// would have an empty domain
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consistent = false;
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break;
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}
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revoke.add(dependent);
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dependent.getDomain().remove(v);
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}
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if (consistent && solve())
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return true;
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// Choosing v as a value lead to a dead end.
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// Revoke all modifications
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field.clearValue();
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for (Field f : revoke)
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f.getDomain().add(v);
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revoke.clear();
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}
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return false;
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}
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public List<Sudoku> solveAll() {
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List<Sudoku> solutions = new ArrayList<>();
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solveAll(solutions);
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return solutions;
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}
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private void solveAll(List<Sudoku> solutions) {
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final Field field = findBestCandidate();
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if (field == null) {
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// A solution has been found
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Sudoku copy = new Sudoku();
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copy.initialize(this.export());
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solutions.add(copy);
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return;
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}
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// There are empty fields. Try all values of its domain
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final List<Field> revoke = new ArrayList<>();
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for (Value v : field.getDomain()) {
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field.setValue(v);
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boolean consistent = true;
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for (Field dependent : field.getDependents())
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if (dependent.getDomain().contains(v)) {
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if (dependent.getDomain().size() == 1) {
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// This is a dead end because field 'dependent'
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// would have an empty domain
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consistent = false;
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break;
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}
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revoke.add(dependent);
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dependent.getDomain().remove(v);
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}
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if (consistent) solveAll(solutions);
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// Revoke all modifications
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field.clearValue();
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for (Field f : revoke)
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f.getDomain().add(v);
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revoke.clear();
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}
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}
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private int[] export() {
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int[] values = new int[SIZE * SIZE];
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int idx = 0;
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while (idx < values.length) {
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Field f = board[idx];
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if (f != null) {
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Value value = f.getValue();
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if (value != null) values[idx] = value.getId();
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else values[idx] = 0;
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}
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else throw new IllegalStateException("at least one field is not set");
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++idx;
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}
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return values;
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}
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}
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68
uebung06/src/sudoku/SudokuApp.java
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68
uebung06/src/sudoku/SudokuApp.java
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package sudoku;
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import java.util.List;
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public class SudokuApp {
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public static void main(String[] args) {
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System.out.println("Sudoku Aufgabenblatt:");
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System.out.println();
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final Sudoku boardBlatt = new Sudoku();
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boardBlatt.initialize(4, 5, 0, 0, 0, 0, 2, 0, 0,
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6, 0, 0, 0, 2, 4, 8, 0, 0,
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8, 0, 0, 0, 6, 1, 3, 0, 0,
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0, 9, 0, 4, 0, 0, 0, 5, 0,
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0, 1, 0, 2, 0, 8, 0, 7, 0,
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0, 3, 0, 0, 0, 9, 0, 8, 0,
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0, 0, 7, 1, 4, 0, 0, 0, 8,
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0, 0, 2, 7, 9, 0, 0, 0, 6,
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0, 0, 5, 0, 0, 0, 0, 2, 1);
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printSolution(boardBlatt);
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System.out.println("Sudoku Handzettel:");
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System.out.println();
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final Sudoku boardHandzettel = new Sudoku();
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boardHandzettel.initialize(7, 0, 0, 0, 2, 5, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 9, 1,
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0, 0, 0, 0, 0, 0, 0, 0, 0,
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4, 0, 9, 1, 0, 0, 0, 0, 0,
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0, 0, 0, 6, 0, 0, 2, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 3, 0,
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8, 2, 0, 0, 0, 0, 5, 0, 0,
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0, 0, 0, 0, 3, 0, 6, 0, 0,
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0, 0, 0, 9, 0, 0, 0, 0, 0);
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printSolution(boardHandzettel);
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System.out.println("Sudoku mit 2 Lösungen:");
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System.out.println();
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final Sudoku boardWithTwoSolutions = new Sudoku();
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boardWithTwoSolutions.initialize(2, 9, 5, 7, 4, 3, 8, 6, 1,
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4, 3, 1, 8, 6, 5, 9, 0, 0,
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8, 7, 6, 1, 9, 2, 5, 4, 3,
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3, 8, 7, 4, 5, 9, 2, 1, 6,
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6, 1, 2, 3, 8, 7, 4, 9, 5,
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5, 4, 9, 2, 1, 6, 7, 3, 8,
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7, 6, 3, 5, 2, 4, 1, 8, 9,
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9, 2, 8, 6, 7, 1, 3, 5, 4,
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1, 5, 4, 9, 3, 8, 6, 0, 0);
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System.out.println(boardWithTwoSolutions);
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System.out.println("Solutions:");
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System.out.println();
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List<Sudoku> solutions = boardWithTwoSolutions.solveAll();
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System.out.println(String.join(System.lineSeparator(), solutions.stream().map(Sudoku::toString).toList()));
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}
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private static void printSolution(Sudoku sudoku) {
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System.out.println(sudoku);
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System.out.println();
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if (sudoku.solve()) {
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System.out.println("Solution:");
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System.out.println();
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System.out.println(sudoku);
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}
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else
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System.out.println("No solution!");
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}
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}
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41
uebung06/src/sudoku/Value.java
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41
uebung06/src/sudoku/Value.java
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@@ -0,0 +1,41 @@
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package sudoku;
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/**
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* The enumeration type of all possible values of a Sudoku field.
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*/
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public enum Value {
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ONE(1), TWO(2), THREE(3), FOUR(4), FIVE(5), SIX(6), SEVEN(7), EIGHT(8), NINE(9);
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private final int id;
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Value(int id) {
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this.id = id;
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}
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/**
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* Returns a string representation of this value. As a matter of fact, its id is returned.
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*
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* @return a string representation of this value.
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*/
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@Override
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public String toString() {
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return String.valueOf(id);
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}
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/**
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* Returns the value with the specified id.
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*
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* @param id an id (1 <= id <= 9)
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* @return the value with the specified id.
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*/
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public static Value of(int id) {
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return values()[id - 1];
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}
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/**
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* Returns the id of this instance.
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*
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* @return the id of this instance.
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*/
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public int getId() {return id;}
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}
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