Valid Sudoku

主要分为三步：行检测，列检测，以及小区域检测

/**
 * Created by jason on 13-12-16.
 */
public class ValidSudoku {

    public boolean isValidSudoku(char[][] board) {
        return isvalidRow(board) && isvalidColumn(board) && isvalidRegieon(board);
    }

    public boolean isvalidRow(char[][] board) {
        int[] count = new int[9];
        for (int i = 0; i < board.length; i++) {
            memset(count, 0);
            for (int j = 0; j < board[0].length; j++) {
                if (!add(board[i][j], count))
                    return false;
            }
        }
        return true;
    }

    public boolean isvalidColumn(char[][] board) {
        int[] count = new int[9];
        for (int i = 0; i < board.length; i++) {
            memset(count, 0);
            for (int j = 0; j < board[0].length; j++) {
                if (!add(board[j][i], count))
                    return false;
            }
        }
        return true;
    }

    public boolean isvalidRegieon(char[][] board) {
        int increment = (int) Math.sqrt(board.length);
        int[] count = new int[9];
        for (int k = 0; k < board.length; k++) {
            memset(count, 0);
            int ii = k / 3 * 3;
            int jj = k % 3 * 3;
            for (int i = ii; i < ii + increment; i++) {
                for (int j = jj; j < jj + increment; j++) {
                    if (!add(board[i][j], count))
                        return false;
                }
            }
        }
        return true;
    }

    public boolean add(char c, int[] count) {
        if (c == '.') return true;
        else return ++count[c - '1'] <= 1;
    }

    public void memset(int[] count, int v) {
        for (int i = 0; i < count.length; i++) {
            count[i] = v;
        }
    }


}