LeetCode：M-36. Valid Sudoku

Link

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.

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

数独规则 ：

There are just 3 rules to Sudoku.

Each row must have the numbers 1-9 occuring just once.

Each column must have the numbers 1-9 occuring just once.

And the numbers 1-9 must occur just once in each of the 9 sub-boxes of the grid.

class Solution {    public boolean isValidSudoku(char[][] board) {        //注意数字是从1~9,所以数组长度9+1=10        boolean[][] rowUsed = new boolean[9][10];//标记行中用过的数字        boolean[][] columnUsed = new boolean[9][10];//标记列中用过的数字        boolean[][] squareUsed = new boolean[9][10];//标记3*3方格中用过的数字                for(int i=0; i<board.length; i++){            for(int j=0; j<board[0].length; j++){                if(board[i][j]!='.'){                    int num = Integer.valueOf(board[i][j]+"");                    int k = i/3*3+j/3;//k表示第几个3*3方格                    if(rowUsed[i][num] || columnUsed[j][num] || squareUsed[k][num])                        return false;                    rowUsed[i][num] = columnUsed[j][num] = squareUsed[k][num] = true;                }            }        }                return true;    }}