# [Leetcode] (python): 037-sudoku Solver

Source: Internet
Author: User

Source of the topic

https://leetcode.com/problems/sudoku-solver/

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

Empty cells is indicated by the character `‘.‘` .

Assume that there would be is only one unique solution.

Test instructions Analysis

Input:a Unsolved Sudoku

Output:a solved Sudoku

Conditions: Meet the Sudoku condition, just need to find an answer

Topic ideas

Using the DFS idea, each empty 1-9 of the choice, if not satisfied then backtracking; the satisfied condition is isvalid (), which satisfies the row, and the column and the small nine squares have not used two identical elements (that is, numbers)

AC Code (PYTHON)

`1 classsolution (object):2     defSolvesudoku (self, Board):3         """4 : Type BOARD:LIST[LIST[STR]]5 : Rtype:void does not return anything, modify board In-place instead.6         """7         defisValid (x, y):8temp =Board[x][y]9Board[x][y] ='R'Ten              forIinchRange (9): One                 ifBoard[i][y] = =Temp: A                     returnFalse -              forIinchRange (9): -                 ifBoard[x][i] = =Temp: the                     returnFalse -              forIinchRange (3): -                  forJinchRange (3): -                     ifBOARD[X/3 * 3 + I][Y/3 * 3 + j] = =Temp: +                         returnFalse -Board[x][y] =Temp +             returnTrue A  at         defDFS (board): -              forIinchRange (9): -                  forJinchRange (9): -                     ifBOARD[I][J] = ='.': -                          forKinch '123456789': -BOARD[I][J] =k in                             ifIsValid (I,J) andDFS (board): -                                 returnTrue toBOARD[I][J] ='.' +                         returnFalse -             returnTrue the              * DFS (board) \$         `

[Leetcode] (python): 037-sudoku Solver

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