LeetCode—sudoku-solver（数独的解法）—java

题目描述：

Write a program to solve a Sudoku puzzle by filling the empty cells.

Empty cells are indicated by the character'.'.

You may assume that there will be only one unique solution.

A sudoku puzzle...

...and its solution numbers marked in red.

思路解析：

• 回溯法，从一条路往前走，能进则进，不能进就后退，换一条路
• 这个问题的解决方法也是一样的，需要从‘1’到‘9’填数字，满足直接返回true；不满足就回退到‘.’
• 遍历每一行，每一列，只要是‘.’的，就要尝试填入‘1’到‘9’
• 注意判断是否是空的条件，首先判断行，i；然后判断列，j；然后判断每个小block是否合法。都判断完毕，就是真正的答案了。

代码：

public class Solution {
    public void solveSudoku(char[][] board) {
        if(board == null||board.length==0)
            return ;
        helper(board);
    }
    private boolean helper(char[][] board){
        for(int i=0;i