LeetCode Sudoku Solver

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.

解数独

对每个空格进行深搜，赋值1-9，并判断该空是否合理

public class Solution {
    public  boolean isVaild(char[][] board, int row, int col) {
		for (int i = 0; i < 9; i++) {    //判断在该行中是否存在
			if (row != i && board[i][col] == board[row][col])
				return false;
		}
		for (int i = 0; i < 9; i++) {    //判断在该列中是否存在
			if (col != i && board[row][i] == board[row][col])
				return false;
		}
		int a = row / 3 * 3;
		int b = col / 3 * 3;
		for (int i = a; i < a + 3; i++) {     //判断在该块中是否存在
			for (int j = b; j < b + 3; j++) {
				if (row != i && col != j && board[i][j] == board[row][col])
					return false;
			}
		}
		return true;
	}

	public  boolean solveSudoku(char[][] board) {
		for (int i = 0; i < 9; i++) {
			for (int j = 0; j < 9; j++) {
				if (board[i][j] == '.'){
					for (int k = 1; k < 10; k++) {
						board[i][j] = (char) (k + '0');
						if (isVaild(board, i, j) && solveSudoku(board))
							return true;
						board[i][j] = '.';
					}
					return false;
				}
			}
		}
		return true;
	}
}