Adding solution of Valid sudoku

Author: Garvit244

1-100q/36.py

@@ -0,0 +1,75 @@
+'''
+Determine if a 9x9 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 9 3x3 sub-boxes of the grid must contain the digits 1-9 without repetition.
+
+A partially filled sudoku which is valid.
+
+The Sudoku board could be partially filled, where empty cells are filled with the character '.'.
+
+Example 1:
+
+Input:
+[
+  ["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
+Example 2:
+
+Input:
+[
+  ["8","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: false
+Explanation: Same as Example 1, except with the 5 in the top left corner being 
+    modified to 8. Since there are two 8's in the top left 3x3 sub-box, it is invalid.
+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.
+The given board contain only digits 1-9 and the character '.'.
+The given board size is always 9x9.
+'''
+
+class Solution(object):
+    def isValidSudoku(self, board):
+        """
+        :type board: List[List[str]]
+        :rtype: bool
+        """
+        import collections
+        dict_row, dict_col, dict_cell = collections.defaultdict(set), collections.defaultdict(set), collections.defaultdict(set)
+        
+        for row_index in range(1, 4):
+            for col_index in range(1, 4):
+                for row in range(3*(row_index-1), 3*row_index):
+                    for col in range(3*(col_index-1), 3*col_index):
+                        cell_data = board[row][col]
+                        if cell_data == '.':
+                            continue
+                        if cell_data in dict_row[row] or cell_data in dict_col[col] or cell_data in dict_cell[(row_index, col_index)]:
+                            return False
+                        
+                        dict_row[row].add(cell_data)
+                        dict_col[col].add(cell_data)
+                        dict_cell[(row_index, col_index)].add(cell_data)
+        
+        return True

README.md

@@ -241,6 +241,7 @@ Python solution of problems from [LeetCode](https://leetcode.com/).
 |40|[Combination Sum II](https://leetcode.com/problems/combination-sum-ii/)| [Python](./1-100q/40.py)|Medium|
 |39|[Combination Sum](https://leetcode.com/problems/combination-sum/)| [Python](./1-100q/39.py)|Medium|
 |38|[Count and Say](https://leetcode.com/problems/count-and-say/)| [Python](./1-100q/38.py)|Easy|
+|36|[Valid Sudoku](https://leetcode.com/problems/valid-sudoku)|[Python](./1-100q/36.py)|Medium|
 |34|[Search for a Range](https://leetcode.com/problems/search-for-a-range/)| [Python](./1-100q/34.py)|Medium|
 |33|[Search in Rotated Sorted Array](https://leetcode.com/problems/search-in-rotated-sorted-array/)| [Python](./1-100q/33.py)|Hard|
 |32|[Longest Valid Parentheses](https://leetcode.com/problems/longest-valid-parentheses/)| [Python](./1-100q/32.py)|Hard|