Added solution for Leetcode Valid Sudoku problem in Python.

Leetcode/Python/valid_sudoku.py

@@ -0,0 +1,61 @@
+"""
+https://leetcode.com/problems/valid-sudoku/submissions/
+
+Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:
+
+Each row must contain the digits 1-9 without repetition.
+Each column must contain the digits 1-9 without repetition.
+Each of the nine 3 x 3 sub-boxes of the grid must contain the digits 1-9 without repetition.
+Note:
+
+A Sudoku board (partially filled) could be valid but is not necessarily solvable.
+Only the filled cells need to be validated according to the mentioned rules.
+
+
+ Example:
+Input: board =
+[["5","3",".",".","7",".",".",".","."]
+,["6",".",".","1","9","5",".",".","."]
+,[".","9","8",".",".",".",".","6","."]
+,["8",".",".",".","6",".",".",".","3"]
+,["4",".",".","8",".","3",".",".","1"]
+,["7",".",".",".","2",".",".",".","6"]
+,[".","6",".",".",".",".","2","8","."]
+,[".",".",".","4","1","9",".",".","5"]
+,[".",".",".",".","8",".",".","7","9"]]
+Output: true
+
+"""
+
+
+class Solution:
+    def isValidSudoku(self, board: list[list[str]]) -> bool:
+        # validating rows
+        for row in board:
+            r = [
+                element for element in row if element != "."
+            ]  # deleting position dots to compare just the numbers
+            if len(r) != len(
+                set(r)
+            ):  # comparting list with set, because the latter has no repeated values
+                return False
+
+        # validating columns
+        for col in range(9):
+            column = [element[col] for element in board]
+            c = [element for element in column if element != "."]
+            if len(c) != len(set(c)):
+                return False
+
+        # validating sub-boxes
+        idx = [0, 3, 6]
+        for i in idx:
+            for p in idx:
+                box = []
+                for element in board[i : i + 3]:
+                    box.extend(element[p : p + 3])
+                b = [element for element in box if element != "."]
+
+                if len(b) != len(set(b)):
+                    return False
+        return True