Palindrome Sudoku Help
Palindrome is marked with blue line. Digits on the palindrome line must read the same from both directions.
Three examples on the grid above:
- 21366312 is read the same in both directions
- 454 is read the same in both directions
- 77 is read the same in both directions
Palindrome Sudoku Solving Strategy
For solving palindromes, we need to look for sibling cells, in other words, cells that have same value on palindrome.
On the grid above yellow cells must have same value, blue cells must have same value and orange cells must have same value. Green cell is independent. If number of cells in palindrome is odd, middle cell is there just to join the palindrome, it doesn't have a sibling cell.
In this case in box one we cannot set number 1, 2 and 3 on the palindrome, which means those candidates can be removed from sibling cells in box 2. In box 2, palindrome cells cannot contain 7, 8 and 9, which means sibling cells in box 1 cannot contain 789. That leaves us with 4, 5 and 6 for first three cells and last three cells on the palindrome.
