CODE 97. Valid Sudoku

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Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules.
The Sudoku board could be partially filled, where empty cells are filled with the character '.'.

A partially filled sudoku which is valid.

public boolean isValidSudoku(char[][] board) {
	// IMPORTANT: Please reset any member data you declared, as
	// the same Solution instance will be reused for each test case.
	for (int i = 0; i < 9; i++) {
		for (int j = 0; j < 9; j++) {
			if (board[i][j] != '.') {
				if (!check(board, i, j)) {
					return false;
				}
			}
		}
	}
	return true;
}

boolean check(char[][] board, int x, int y) {
	for (int i = 0; i < 9; i++) {
		if (i != y && board[x][i] == board[x][y]) {
			return false;
		}
	}
	for (int i = 0; i < 9; i++) {
		if (i != x && board[i][y] == board[x][y]) {
			return false;
		}
	}
	for (int i = 3 * (x / 3); i < 3 * (x / 3 + 1); i++) {
		for (int j = 3 * (y / 3); j < 3 * (y / 3 + 1); j++) {
			if (i != x && j != y && board[i][j] == board[x][y]) {
				return false;
			}
		}
	}
	return true;
}