docs: add new problem documentation pages and update redirects

apps/docs/content/(02-nodal-grid)/matrix-index-math/36_valid-sudoku.mdx

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+---
+title: '36. Valid Sudoku'
+description: 'Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:'
+icon: dot
+topics:
+  - { name: "Array", slug: "array" }
+  - { name: "Hash Table", slug: "hash-table" }
+  - { name: "Matrix", slug: "matrix" }
+issue: "https://github.com/prdlk/leetcode/issues/94"
+sidebar:
+  label: 'Valid Sudoku'
+  badge: 'Medium'
+---
+
+### Example 1:
+- 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`
+
+### Example 2:
+- Input: `board = [["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.
+
+### Constraints:
+
+- `board.length == 9`
+- `board[i].length == 9`
+- board[i][j] is a digit 1-9 or '.'.
+
+## Solution
+
+```py
+import collections
+
+
+class Solution:
+    def isValidSudoku(self, board: list[list[str]]) -> bool:
+        cols = collections.defaultdict(set)
+        rows = collections.defaultdict(set)
+        squares = collections.defaultdict(set)  # (r/3, c/3)
+
+        for r in range(9):
+            for c in range(9):
+                if board[r][c] == ".":
+                    continue
+                if (
+                    board[r][c] in rows[r]
+                    or board[r][c] in cols[c]
+                    or board[r][c] in squares[(r // 3, c // 3)]
+                ):
+                    return False
+                cols[c].add(board[r][c])
+                rows[r].add(board[r][c])
+                squares[(r // 3, c // 3)].add(board[r][c])
+
+        return True
+```