Time: 4 ms (60.78%), Space: 17.4 MB (12.03%) - LeetHub

0036-valid-sudoku/0036-valid-sudoku.py

@@ -1,17 +1,50 @@
 class Solution:
     def isValidSudoku(self, board: List[List[str]]) -> bool:
-        rows = collections.defaultdict(set)
-        cols = collections.defaultdict(set)
-        boxes = collections.defaultdict(set)
+        column_cache = dict()
+        board_cache  = dict()
+
         for r in range(len(board)):
-            for c in range(len(board[1])):
+            row = r + 1
+            row_cache = set()
+
+            for c in range(len(board[r])):
                 val = board[r][c]
-                if val == '.': continue
-                if (val in rows[r] or
-                    val in cols[c] or
-                    val in boxes[(r // 3, c // 3)]): return False
-                rows[r].add(val)
-                cols[c].add(val)
-                boxes[(r // 3, c // 3)].add(val)
+                if val == ".":
+                    continue
+
+                col     = c + 1
+                board_n = self.getBoard(row, col)
+                column_cache[col]    = column_cache.get(col, set())
+                board_cache[board_n] = board_cache.get(board_n, set())
 
-        return True
+                if val in row_cache or val in column_cache[col] or val in board_cache[board_n]:
+                    return False
+
+                row_cache.add(val)
+                column_cache[col].add(val)
+                board_cache[board_n].add(val)
+
+        return True
+
+    def getBoard(self, row: int, column: int) -> int:
+        if row in {1, 2, 3}:
+            if column in {1, 2, 3}:
+                return 1
+            elif column in {4, 5, 6}:
+                return 2
+            elif column in {7, 8, 9}:
+                return 3
+        if row in {4, 5, 6}:
+            if column in {1, 2, 3}:
+                return 4
+            elif column in {4, 5, 6}:
+                return 5
+            elif column in {7, 8, 9}:
+                return 6
+        if row in {7, 8, 9}:
+            if column in {1, 2, 3}:
+                return 7
+            elif column in {4, 5, 6}:
+                return 8
+            elif column in {7, 8, 9}:
+                return 9