《Java语言程序设计（进阶篇）》 课后习题第22章代码chapter22.rar

import java.util.ArrayList; import javafx.application.Application; import javafx.geometry.Pos; import javafx.scene.Scene; import javafx.scene.control.Button; import javafx.scene.control.Label; import javafx.scene.control.TextField; import javafx.scene.layout.BorderPane; import javafx.scene.layout.GridPane; import javafx.scene.layout.HBox; import javafx.stage.Stage; public class Exercise22_25 extends Application { public static final int SIZE = 10; private TextField[][] cells = new TextField[SIZE][SIZE]; private Button btSolve = new Button("Solve"); private Button btClear = new Button("Clear"); private Button btNext = new Button("Next"); private Label lblStatus = new Label(); private static ArrayList<int[][]> list = new ArrayList<>(); private int currentSolutionIndex = 0; @Override // Override the start method in the Application class public void start(Stage primaryStage) { GridPane[][] panels = new GridPane[3][3]; GridPane p1 = new GridPane(); p1.setStyle("-fx-border-color: red"); for (int i = 0; i < 3; i++) { for (int j = 0; j < 3; j++) { p1.add(panels[i][j] = new GridPane(), j, i); panels[i][j].setStyle("-fx-border-color: red"); } } for (int i = 0; i < 9; i++) { for (int j = 0; j < 9; j++) { panels[i / 3][j / 3].add(cells[i][j] = new TextField(), j % 3, i % 3); cells[i][j].setPrefColumnCount(1); } } HBox hBox = new HBox(5); hBox.getChildren().addAll(btSolve, btClear, btNext); hBox.setAlignment(Pos.CENTER); btNext.setVisible(false); BorderPane pane = new BorderPane(); pane.setCenter(p1); pane.setBottom(hBox); pane.setTop(lblStatus); BorderPane.setAlignment(lblStatus, Pos.CENTER); // Create a scene and place it in the stage Scene scene = new Scene(pane, 240, 280); primaryStage.setTitle("Exercise22_25"); // Set the stage title primaryStage.setScene(scene); // Place the scene in the stage primaryStage.show(); // Display the stage btSolve.setOnAction(e -> solve()); btClear.setOnAction(e -> { lblStatus.setText(""); btNext.setVisible(false); for (int i = 0; i < 9; i++) for (int j = 0; j < 9; j++) { cells[i][j].setText(""); cells[i][j].setStyle("-fx-text-fill: black"); } }); btNext.setOnAction(e -> { currentSolutionIndex = ++currentSolutionIndex % list.size() ; lblStatus.setText(currentSolutionIndex + 1 + "/" + list.size()); int[][] solutionGrid = list.get(currentSolutionIndex); for (int i = 0; i < 9; i++) { for (int j = 0; j < 9; j++) { cells[i][j].setText(solutionGrid[i][j] + ""); } } }); } private void solve() { list.clear(); currentSolutionIndex = 0; int[][] grid = new int[9][9]; for (int i = 0; i < 9; i++) { for (int j = 0; j < 9; j++) { if (cells[i][j].getText().trim().length() == 0) { grid[i][j] = 0; } else { grid[i][j] = Integer.parseInt(cells[i][j].getText()); cells[i][j].setStyle("-fx-text-fill: gray"); } } } if (!Sudoku.isValid(grid)) { lblStatus.setText("Invalid Input"); } else { int count = Sudoku.search(grid); if (count == 0) { lblStatus.setText("No solution"); } else { // Display the first solution int[][] solutionGrid = list.get(0); for (int i = 0; i < 9; i++) { for (int j = 0; j < 9; j++) { cells[i][j].setText(solutionGrid[i][j] + ""); } } } } if (list.size() > 1) { btNext.setVisible(true); lblStatus.setText("1/" + list.size() + " solutions"); } } /** * The main method is only needed for the IDE with limited * JavaFX support. Not needed for running from the command line. */ public static void main(String[] args) { launch(args); } public static class Sudoku { /** Obtain a list of free cells from the puzzle */ public static int[][] getFreeCellList(int[][] grid) { // 81 is the maximum number of free cells int[][] tempList = new int[81][2]; int numberOfFreeCells = 0; for (int i = 0; i < 9; i++) for (int j = 0; j < 9; j++) if (grid[i][j] == 0) { tempList[numberOfFreeCells][0] = i; tempList[numberOfFreeCells][1] = j; numberOfFreeCells++; } // Trim freeCellList int[][] freeCellList = new int[numberOfFreeCells][2]; for (int i = 0; i < numberOfFreeCells; i++) { freeCellList[i][0] = tempList[i][0]; freeCellList[i][1] = tempList[i][1]; } return freeCellList; } /** Search for up to 3 solutions. * This method returns the number of solutions found. * Possible return values are 0, 1, 2, and 3. */ public static int search(int[][] grid) { int[][] freeCellList = getFreeCellList(grid); // Free cells int k = 0; // Start from the first free cell int count = 0; // Multiple solutions: Count for 3 solutions boolean done = false; while (!done) { int i = freeCellList[k][0]; int j = freeCellList[k][1]; if (grid[i][j] == 0) grid[i][j] = 1; // Start with 1 if (isValid(i, j, grid)) { if (k + 1 == freeCellList.length) { // No more free cells // A solution is found count++; int[][] solutionGrid = new int[9][9]; for (int i1 = 0; i1 < 9; i1++) for (int j1 = 0; j1 < 9; j1++) solutionGrid[i1][j1] = grid[i1][j1]; list.add(solutionGrid); // Now search for the next possible solution if (grid[i][j] < 9) { grid[i][j] = grid[i][j] + 1; // Check the next possible value } else { // grid[i][j] is 9, backtrack while (grid[i][j] == 9) { grid[i][j] = 0; // Reset to free cell if (k == 0) { done = true; // No possible value any more, done! return count; } k--; // Backtrack i = freeCellList[k][0]; j = freeCellList[k][1]; } grid[i][j] = grid[i][j] + 1; // Check the next possible value } } else { // Move to the next free cell k++; } } else if (grid[i][j] < 9) { grid[i][j] = grid[i][j] + 1; // Check the next possible value } else { // grid[i][j] is 9, backtrack while (grid[i][j] == 9) { grid[i][j] = 0; // Reset to free cell if (k == 0) { return count; // No possible value } k--; // Backtrack i = freeCellList[k][0]; j = freeCellList[k][1]; } grid[i][j] = grid[i][j] + 1; // Check the next possible value } } return count; // A solution is found } /** Check whether grid[i][j] is valid in the grid */ public static boolean isValid(int i, int j, int[][] grid) { // Check whether grid[i][j] is valid at the i's row for (int column = 0; column < 9; column++) if (column != j && grid[i][column] == grid[i][j]) return false; // Check whether grid[i][j] is valid at the j's column for (int row = 0; row < 9; row++) if (row != i && grid[row][j] == grid[i][j]) return false; // Check whether grid[i][j] is valid in the 3 by 3 box fo