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。
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; }}