[LintCode] Valid Sudoku [数独]

Problem

Determine whether a Sudoku is valid.

The Sudoku board could be partially filled, where empty cells are filled with the character '.'.

Example

The following partially filed sudoku is valid.

Note

写两个for循环遍历矩阵中所有的字符，若不是'.'且不满足数独规则isvalid()，则返回false。
对于给定坐标的字符，写一个数独规则的函数isvalid()判读在某些范围内是否有重复值出现，先比较行，再比较列，最后比较每个小九方格。

Solution

class Solution {
    public boolean isValidSudoku(char[][] board) {
        for (int i = 0; i < board.length; i++) {
            for (int j = 0; j < board[0].length; j++) {
                if (board[i][j] != '.' && !isvalid(board, i, j)) return false;
            }
        }
        return true;
    }
    public boolean isvalid(char[][] board, int row, int col) {
        for (int i = 0; i < board.length; i++) {
            if (board[row][col] == board[i][col] && row != i) return false;
        }
        for (int i = 0; i < board[0].length; i++) {
            if (board[row][col] == board[row][i] && col != i) return false;
        }
        for (int i = row/3*3; i < row/3*3+3; i++) {
            for (int j = col/3*3; j < col/3*3+3; j++) {
                if (board[i][j] == board[row][col] && !(i == row && j == col)) return false;
            }
        }
        return true;
    }
}