Medium Palindrome Sudoku
7
1
2
6
8
6
2
9
3
9
7
8
9
7
5
8
6
2
8
3
7
5
6
1
3
1
3
9
2
7
8
9
How to play Palindrome Sudoku
Standard Sudoku rules apply. Each grey line is a palindrome - The sequence of digits reads the same from both ends. For a 5-cell line reading 3,7,5,7,3, position 1 = position 5 and position 2 = position 4.
About Palindrome Sudoku
Difficulty
★★★☆☆
3/5
Constraint Type
Line Constraints
Typical Givens
20–28
Avg. Solve (Medium)
16 min
Palindrome Sudoku marks lines on the grid whose digit sequence must be a palindrome — reading the same in both directions. If a line has cells A-B-C-D-E, then A=E and B=D, while C is the central digit. This creates pairs of cells that must share the same value, acting as powerful equality constraints across the grid.
Solving Techniques
| Technique | Description | Level |
|---|---|---|
| Mirror Pair Identification | In a palindrome of length L, cell i and cell L+1−i must share the same digit. Identify all mirror pairs before solving. | Beginner |
| Centre Cell Freedom | The central cell of an odd-length palindrome has no mirror constraint — it is only restricted by standard row/column/box rules. | Beginner |
| Mirror Propagation | Once one cell of a mirror pair is determined, immediately set its partner to the same value. | Intermediate |
| Multi-Palindrome Intersection | If two palindromes share a cell, that cell must satisfy both palindrome relationships simultaneously. | Advanced |
Average Solve Time by Difficulty
Easy
7 min
Medium
16 min
Hard
32 min
Expert
58 min