class Solution {

    void reset(int[] numbers) {
        for (int i = 0; i < numbers.length; i++) {
            numbers[i] = 0;
        }
    }

    boolean isValid(int[] numbers, char current) {
        if (current != '.') {
            int number = current - '0';
            if (numbers[number - 1] > 0) {
                return false;
            }
            numbers[number - 1]++;
        }

        return true;
    }

    public boolean isValidSudoku(char[][] board) {

        int[] numbers = new int[9];

        // rows
        for (int row = 0; row < 9; row++) {
            reset(numbers);
            for (int col = 0; col < 9; col++) {
                if (!isValid(numbers, board[row][col])) {
                    return false;
                }
            }
        }

        // columns
        for (int col = 0; col < 9; col++) {
            reset(numbers);
            for (int row = 0; row < 9; row++) {
                if (!isValid(numbers, board[row][col])) {
                    return false;
                }
            }
        }

        // box sections
        reset(numbers);
        for (int boxR = 0; boxR < 9; boxR += 3) {
            for (int boxC = 0; boxC < 9; boxC += 3) {
                reset(numbers);
                for (int row = boxR; row < boxR + 3; row++) {
                    for (int col = boxC; col < boxC + 3; col++) {
                        if (!isValid(numbers, board[row][col])) {
                            return false;
                        }
                    }
                }
            }
        }

        return true;
    }
}