回文數獨
8
2
3
1
4
1
5
5
4
9
7
6
7
2
2
1
7
9
9
5
1
8
2
7
9
4
5
6
4
1
2
8
6
2
7
1
9
4
沿著一條線的 digit sequence 向前和向後讀取相同
什麼是 回文數獨？
Palindrome Sudoku 在網格上標記線條，其數字序列必須是回文——雙向讀取相同。如果一條線條有單元格 A-B-C-D-E，則 A=E 且 B=D，而 C 是中心數字。這創造了必須共享相同數值的單元格對，充當網格中的強大相等約束。
一覽
| 約束類型 | 線條約束 |
| 典型給定數 | 20–28 |
| 難度評分 | ★★★☆☆ 3/5 |
| 平均解題時間 — 簡單 | 7分鐘 |
| 平均解題時間 — 中等 | 16分鐘 |
| 平均解題時間 — 困難 | 32分鐘 |
| 平均解題時間 — 專家 | 58分鐘 |
如何解 回文數獨
| 技巧 | 它的作用 | 等級 |
|---|---|---|
| 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. | 進階 |
| 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. | 進階 |
| Mirror Propagation | Once one cell of a mirror pair is determined, immediately set its partner to the same value. | 進階 |
| Multi-Palindrome Intersection | If two palindromes share a cell, that cell must satisfy both palindrome relationships simultaneously. | 進階 |
平均解題時間
簡單
7分鐘
中等
16分鐘
困難
32分鐘
專家
58分鐘
常見問題
什麼是 Palindrome Sudoku？
Palindrome Sudoku is a variant where grey lines are drawn across the grid. Every grey line must read the same forwards and backwards — meaning the first cell mirrors the last, the second mirrors the second-to-last, and so on. Standard Sudoku rules apply throughout.
How does the palindrome constraint work?
For any palindrome line, cell positions are mirrored around the centre. On a 6-cell line, cells 1 and 6 hold the same digit, cells 2 and 5 hold the same digit, and cells 3 and 4 hold the same digit. This immediately links distant parts of the grid — placing a digit at one end fixes the digit at the other end.
Can palindrome lines have repeated digits?
Yes, palindrome lines inherently require digit repetition — each mirrored pair shares the same digit. However, standard Sudoku rules still apply, so a repeated digit must be in different rows, columns, and boxes. Palindrome lines are carefully constructed so that this repetition is always consistent with uniqueness rules.
Is Palindrome Sudoku harder than regular Sudoku?
Easy palindrome puzzles are often easier than classic Sudoku because the mirroring immediately links cells across the board, providing extra deductions. Harder difficulties become quite challenging because you must track mirrored constraints across long lines while maintaining standard Sudoku logic.
What is the best first move in Palindrome Sudoku?
Find palindrome lines where one endpoint cell is already constrained by its row, column, or box. Placing a digit there immediately fixes the mirrored cell at the other end. Also look for odd-length lines — the centre cell has no mirror partner, so it's only constrained by standard Sudoku rules.
How long does Palindrome Sudoku take to solve?
Easy puzzles take 8–15 minutes. Medium puzzles run 15–30 minutes. Hard puzzles average 30–60 minutes and expert puzzles often exceed 90 minutes. The difficulty increases sharply when multiple long palindrome lines overlap across the same region of the grid.