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题目来源
https://leetcode.com/problems/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.
题意分析
Input:a unsolved Sudoku
Output: a solved Sudoku
Conditions:满足数独条件，只需要找到一个答案
题目思路
用dfs的思路，对每一个空进行1-9的选择，如果不满足则回溯；满足条件为isValid（），就是满足该行，该列以及该小九方格没有使用过两个一样的元素（即数字）
AC代码（Python）
1 class Solution(object): 2 def solveSudoku(self, board): 3 """ 4 :type board: List[List[str]] 5 :rtype: void Do not return anything, modify board in-place instead. 6 """ 7 def isValid(x, y): 8 temp = board[x][y] 9 board[x][y] = ‘r‘ 10 for i in range(9): 11 if board[i][y] == temp: 12 return False 13 for i in range(9): 14 if board[x][i] == temp: 15 return False 16 for i in range(3): 17 for j in range(3): 18 if board[x / 3 * 3 + i][y / 3 * 3 + j] == temp: 19 return False 20 board[x][y] = temp 21 return True 22 23 def dfs(board): 24 for i in range(9): 25 for j in range(9): 26 if board[i][j] == ‘.‘: 27 for k in ‘123456789‘: 28 board[i][j] = k 29 if isValid(i,j) and dfs(board): 30 return True 31 board[i][j] = ‘.‘ 32 return False 33 return True 34 35 dfs(board) 36
[LeetCode]题解（python）：037-Sudoku Solver
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原文地址：http://www.cnblogs.com/loadofleaf/p/5042804.html
