[Leetcode] Valid Sudoku

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.

 

Solution:

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.

 

一个valid的sudoku只有3个条件：横、竖、小方块内部   满足条件即可。

我老想成还需要对角线上的数也满足条件，这样想是错的！！！

public 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]=='.'){
                    continue;
                }else{
                    char temp=board[i][j];
                    board[i][j]='C';                       //通过将board[i][j]的值改为board内部的其他位置的数
                    boolean b=isValid(board,i,j,temp);     //不可能取到的值来方便后边儿的验证。
                    board[i][j]=temp;
                    if(b==false)
                        return false;
                }
            }
        }
        return true;
    }

    private boolean isValid(char[][] board, int x, int y, char temp) {
        // TODO Auto-generated method stub
        for(int i=0;i<board.length;++i){           //竖着的
            if(board[i][y]==temp)
                return false;
        }
        for(int i=0;i<board[0].length;++i){        //横着的
            if(board[x][i]==temp){
                return false;
            }
        }
        for(int i=(x/3)*3;i<(x/3+1)*3;++i){        //小方块内部的
            for(int j=(y/3)*3;j<(y/3+1)*3;++j){    //判断好属于哪块小方格
                if(board[i][j]==temp)
                    return false;
            }
        }
        return true;
    }
}