*8.24 (Check Sudoku solution) Listing 8.4 checks whether a solution is valid by checking
whether every number is valid in the board. Rewrite the program by checking
whether every row, every column, and every small box has the numbers 1 to 9.
import java.util.Scanner; public class ProgrammingEx8_24 { public static void main(String[] args) { // Read a Sudoku solution int[][] grid = readASolution(); System.out.println(isValid(grid) ? "Valid solution" : "Invalid solution"); } private static boolean isValid(int[][] grid) { return checkBlocks(grid) && checkRow(grid) && checkCol(grid); } /** Read a Sudoku solution from the console */ public static int[][] readASolution() { // Create a Scanner Scanner input = new Scanner(System.in); System.out.println("Enter a Sudoku puzzle solution:"); int[][] grid = new int[9][9]; for (int i = 0; i < 9; i++) for (int j = 0; j < 9; j++) grid[i][j] = input.nextInt(); return grid; } public static boolean checkBlocks( int n[][]) { for (int i = 0; i < n.length; i+=3) { for (int j = 0; j < n[i].length; j+=3) { if (!checkBlock(i,j,n)){ return false; } } } return true; } public static boolean checkBlock(int row, int col, int[][] n) { int[] seq = new int[9]; for (int i = 0; i < seq.length; i++) { seq[i] = n[i/3][i%3]; } return checkSeq(seq); } public static boolean checkRow(int n[][]) { int[] seq = new int[9]; for (int i = 0; i < n.length; i++) { for (int j = 0; j < n.length; j++) { seq[j] = n[i][j]; } if(!checkSeq(seq)) { return false; } } return true; } public static boolean checkCol(int n[][]) { int[] seq = new int[9]; for (int i = 0; i < n.length; i++) { for (int j = 0; j < n.length; j++) { seq[j] = n[j][i]; } if(!checkSeq(seq)) { return false; } } return true; } //Check a sequence of 9 numbers if it contain number 1-9 public static boolean checkSeq(int n[]) { boolean[] tray = new boolean [n.length]; boolean result =true; for (int i = 0; i < tray.length; i++) { tray[n[i]-1] = true; } for (int j = 0; j < tray.length; j++) { result &= tray[j]; } return result; } }
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