Java程序设计基础篇（第8版）第七章编程题答案

package excercise7_20; import java.util.Scanner; public class Code { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub char[][] board = new char[6][7]; displayBoard(board); while (true) { // Prompt the first player dropADisc('R', board); displayBoard(board); if (isWon(board)) { System.out.println("The red player won"); System.exit(0); } else if (isDraw(board)) { System.out.println("No winner"); System.exit(0); } // Prompt the second player dropADisc('Y', board); displayBoard(board); if (isWon(board)) { System.out.println("The yellow player won"); System.exit(0); } else if (isDraw(board)) { System.out.println("No winner"); System.exit(0); } } } public static void dropADisc(char player, char[][] board) { Scanner input = new Scanner(System.in); boolean done = false; do { System.out.print("Drop a " + (player == 'R' ? "red" : "yellow") + " disk at column (0 - 6): "); int column = input.nextInt(); if (placeADisk(board, column, player)) { done = true; } else System.out.println("The column is full. Try a different column"); } while (!done); } public static boolean placeADisk(char[][] board, int column, char player) { for (int i = 0; i < board.length; i++) { if (board[i][column] == '\u0000') { board[i][column] = player; return true; // successful } } return false; // full, unsuccessful } public static void displayBoard(char[][] board) { for (int i = board.length - 1; i >= 0 ; i--) { System.out.print("|"); for (int j = 0; j < board[i].length; j++) { System.out.print(board[i][j] != '\u0000' ? board[i][j] + "|" : " |"); } System.out.println(); } System.out.println("----------------------"); } public static boolean isWon(char[][] board) { return isConsecutiveFour(board); } public static boolean isDraw(char[][] board) { for (int i = 0; i < board.length; i++) { for (int j = 0; j < board[i].length; j++) { if (board[i][j] == '\u0000') return false; } } return true; // All cells are now occupied } public static boolean isConsecutiveFour(char[][] values) { int numberOfRows = values.length; int numberOfColumns = values[0].length; // Check rows for (int i = 0; i < numberOfRows; i++) { if (isConsecutiveFour(values[i])) return true; } // Check columns for (int j = 0; j < numberOfColumns; j++) { char[] column = new char[numberOfRows]; // Get a column into an array for (int i = 0; i < numberOfRows; i++) { column[i] = values[i][j]; } if (isConsecutiveFour(column)) return true; } // Check major diagonal (lower part) for (int i = 0; i < numberOfRows - 3; i++) { int numberOfElementsInDiagonal = Math.min(numberOfRows - i, numberOfColumns); char[] diagonal = new char[numberOfElementsInDiagonal]; for (int k = 0; k < numberOfElementsInDiagonal; k++) { diagonal[k] = values[k + i][k]; } if (isConsecutiveFour(diagonal)) return true; } // Check major diagonal (upper part) for (int j = 1; j < numberOfColumns - 3; j++) { int numberOfElementsInDiagonal = Math.min(numberOfColumns - j, numberOfRows); char[] diagonal = new char[numberOfElementsInDiagonal]; for (int k = 0; k < numberOfElementsInDiagonal; k++) { diagonal[k] = values[k][k + j]; } if (isConsecutiveFour(diagonal)) return true; } // Check sub-diagonal (left part) for (int j = 3; j < numberOfColumns; j++) { int numberOfElementsInDiagonal = Math.min(j + 1, numberOfRows); char[] diagonal = new char[numberOfElementsInDiagonal]; for (int k = 0; k < diagonal.length; k++) { diagonal[k] = values[k][j - k]; } if (isConsecutiveFour(diagonal)) return true; } // Check sub-diagonal (right part) for (int i = 1; i < numberOfRows - 3; i++) { int numberOfElementsInDiagonal = Math.min(numberOfRows - i, numberOfColumns); char[] diagonal = new char[numberOfElementsInDiagonal]; for (int k = 0; k < diagonal.length; k++) { diagonal[k] = values[k + i][numberOfColumns -k - 1]; } if (isConsecutiveFour(diagonal)) return true; } return false; } public static boolean isConsecutiveFour(char[] values) { for (int i = 0; i < values.length - 3; i++) { boolean isEqual = true; for (int j = i; j < i + 3; j++) { if (values[j] == '\u0000' || values[j] != values[j + 1]) { isEqual = false; break; } } if (isEqual) return true; } return false; } }