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Author: assassint2017

Sudoku Solver/Sudoku_Solver.py

@@ -0,0 +1,53 @@
+# 532ms 55.56%
+class Solution:
+    def solveSudoku(self, board):
+        """
+        :type board: List[List[str]]
+        :rtype: void Do not return anything, modify board in-place instead.
+        """
+        self.board = board
+        self.solve()
+    
+    def find_first_unassigned(self):
+        """
+        
+        顺序查找第一个还没有被赋值的坐标
+        """
+        for i in range(9):
+            for j in range(9):
+                if self.board[i][j] == '.':
+                    return i, j
+        # 如果全部被赋值，则返回一个哑变量
+        return -1, -1
+        
+    def judge(self, row, column, value):
+        """
+        
+        用来判断给定坐标的值是否合理
+        """
+        # 首先判断行
+        if value in self.board[row]:
+            return False
+        # 然后判断列
+        for i in range(9):
+            if self.board[i][column] == value:
+                return False
+        # 最后判断宫
+        for i in range(row // 3 * 3, row // 3 * 3 + 3):
+            for j in range(column // 3 * 3, column // 3 * 3 + 3):
+                if self.board[i][j] == value:
+                    return False
+        # 如果都通过了测试，则返回真
+        return True
+    
+    def solve(self):
+        row, column = self.find_first_unassigned()
+        if row == - 1 and column == -1:
+            return True
+        for num in ["1","2","3","4","5","6","7","8","9"]:
+            if self.judge(row, column, num):
+                self.board[row][column] = num
+                if self.solve():
+                    return True
+                self.board[row][column] = '.'
+        return False