[Leetcode] valid Sudoku

Determine if a Sudoku is valid, according to: Sudoku puzzles-the rules.

The sudoku board cocould be partially filled, where empty cells are filled with the character '.'.

A partially filled Sudoku which is valid.

Note:
A valid Sudoku Board (partially filled) is not necessarily solvable. Only the filled cells need to be validated.

Https://oj.leetcode.com/problems/valid-sudoku/

Train of Thought: according to the rules, first check the row, then check the column, and then check the 9 cells.

public class Solution {public boolean isValidSudoku(char[][] board) {int i;for (i = 0; i < 9; i++) {if (!isValid(board, i, i + 1, 0, 9))return false;}int j;for (j = 0; j < 9; j++) {if (!isValid(board, 0, 9, j, j + 1))return false;}for (i = 0; i < 9; i = i + 3)for (j = 0; j < 9; j = j + 3) {if (!isValid(board, i, i + 3, j, j + 3))return false;}return true;}private boolean isValid(char[][] board, int iBegin, int iEnd, int jBegin,int jEnd) {HashSet<Character> set = new HashSet<Character>();for (int i = iBegin; i < iEnd; i++)for (int j = jBegin; j < jEnd; j++) {if (set.contains(board[i][j]))return false;else if (board[i][j] != ‘.‘)set.add(board[i][j]);}return true;}public static void main(String[] args) {char[][] board = { { ‘5‘, ‘3‘, ‘.‘, ‘.‘, ‘7‘, ‘.‘, ‘.‘, ‘.‘, ‘.‘ },{ ‘6‘, ‘.‘, ‘.‘, ‘1‘, ‘9‘, ‘5‘, ‘.‘, ‘.‘, ‘.‘ },{ ‘.‘, ‘9‘, ‘8‘, ‘.‘, ‘.‘, ‘.‘, ‘.‘, ‘6‘, ‘.‘ },{ ‘8‘, ‘.‘, ‘.‘, ‘.‘, ‘6‘, ‘.‘, ‘.‘, ‘.‘, ‘3‘ },{ ‘4‘, ‘.‘, ‘.‘, ‘8‘, ‘.‘, ‘3‘, ‘.‘, ‘.‘, ‘1‘ },{ ‘7‘, ‘.‘, ‘.‘, ‘.‘, ‘2‘, ‘.‘, ‘.‘, ‘.‘, ‘6‘ },{ ‘.‘, ‘6‘, ‘.‘, ‘.‘, ‘.‘, ‘.‘, ‘2‘, ‘8‘, ‘.‘ },{ ‘.‘, ‘.‘, ‘.‘, ‘4‘, ‘1‘, ‘9‘, ‘.‘, ‘.‘, ‘5‘ },{ ‘.‘, ‘.‘, ‘.‘, ‘.‘, ‘8‘, ‘.‘, ‘.‘, ‘7‘, ‘9‘ } };System.out.println(new Solution().isValidSudoku(board));}}