題目描述

基本思路

DFS必須得掌握啊

實現程式碼

class Solution:
    def solveSudoku(self, board):
        """
        :type board: List[List[str]]
        :rtype: void Do not return anything, modify board in-place instead.
        """
        def isValid(x,y):
            tmp=board[x][y]
            board[x][y]='D'
            for i in range(9):
                if board[i][y]==tmp: 
                    return False
            for i in range(9):
                if board[x][i]==tmp: 
                    return False
            for i in range(3):
                for j in range(3):
                    if board[(x//3)*3+i][(y//3)*3+j]==tmp: 
                        return False
            board[x][y]=tmp
            return True
        
        def dfs(board):
            for i in range(9):
                for j in range(9):
                    if board[i][j]=='.':
                        for k in '123456789':
                            board[i][j]=k
                            if isValid(i,j) and dfs(board):
                                return True
                            board[i][j]='.'
                        return False
            return True
        dfs(board)