feat: 37.解数独补充python代码

Author: suukii

basic/hashmap/24.sudoku-solver.md

@@ -143,3 +143,48 @@ var solveSudoku = function (board) {
     }
 };
 ```
+
+Python Code
+
+```py
+class Solution(object):
+    def solveSudoku(self, board):
+        """
+        :type board: List[List[str]]
+        :rtype: None Do not return anything, modify board in-place instead.
+        """
+        rows = [[False]*9 for _ in range(9)]
+        cols = [[False]*9 for _ in range(9)]
+        boxes = [[[False]*9 for _ in range(3)] for _ in range(3)]
+
+        def mark(x, y, n, status):
+            rows[x][n] = cols[y][n] = boxes[x // 3][y // 3][n] = status
+
+        def valid(x, y, n):
+            return (not rows[x][n]) and (not cols[y][n]) and (not boxes[x // 3][y // 3][n])
+
+        def dfs(pos):
+            if pos >= len(spaces): return True
+
+            x, y = spaces[pos]
+            for n in range(9):
+                if not valid(x, y, n): continue
+
+                board[x][y] = str(n + 1)
+                mark(x, y, n, True)
+
+                if dfs(pos + 1): return True
+
+                mark(x, y, n, False)
+
+        spaces = []
+        for x in range(9):
+            for y in range(9):
+                cell = board[x][y]
+
+                if cell == '.':
+                    spaces.append((x, y))
+                else:
+                    mark(x, y, int(cell) - 1, True)
+        dfs(0)
+```