Note: Identical letters cannot be next to one another in the grid either horizontally or vertically, but may be adjacent diagonally.
+---+---+---+---+---+
A | 1 | 1 | 1 | 1 | 2 |
+---+---+---+---+---+
B | 2 | 1 | 3 | 1 | 1 |
+---+---+---+---+---+
C | 1 | 2 | 1 | 1 | 0 |
+---+---+---+---+---+
A B C D | 1 | 1 | 0 | 2 | 2 |
+---+---+---+---++===+===+===+===+===+
| 2 | 1 | 1 | 1 || | | | | |
+---+---+---+---++---+---+---+---+---+
| 1 | 2 | 0 | 2 || | | | | |
+---+---+---+---++---+---+---+---+---+
| 1 | 2 | 1 | 1 || | | | | |
+---+---+---+---++---+---+---+---+---+
| 1 | 0 | 2 | 2 || | | | | |
+---+---+---+---++---+---+---+---+---+
| 1 | 3 | 1 | 0 || | | | | |
+---+---+---+---++---+---+---+---+---+
From Mensa 365 Brain Puzzlers for 2015, by Mark Danna and Fraser Simpson, Workman Publishing, New York, puzzle for December 7.
