回文 Palindrome

标准数独基础上，线条上数字是回文。回文是一种文学体裁，无论从哪个方向上阅读，都是一样的序列。

Classic rules applied, additionally, numbers are palindrome on lines. Palindrome is a literary genre, it's same sequence whether the direction of reading. 

它本质上是克隆数独，但有细微的差别。如果线条上有偶数格，那就是克隆；如果有奇数格，那么最中间的单元格是无用的信息。此外，九阶的回文数独里，最长的回文有73格。

It's essentially Clone, but there's tiny difference. If the line has even cells, that will be a Clone; if the line has odd cells, the center of the line is an useless information. Additionally, the longest palindrome line in Palindrome 9x9 have 73 cells.

◆可以利用如同克隆数独的方式解决。

Some cases can be deal with ways like Clone.

练习 Practice

① 观察例题 Observe this example.

(a) 题目中有多少对克隆对？How many clone pairs in this puzzle?

(b) 解答问号格 Find out the ？cell.

答案 Answer

① (a) 8 (b) C4=5.