额外区域 Extra Regions

标准数独基础上，每个区域内的数字不能重复。

Classic rules applied, additionally, numbers cannot repeat in each colored region.

绝大多数题目有两个不重叠的区域。但是在一些特殊案例中，N阶题目可能有N个区域。

Most puzzles have two regions with no public cells. But in some special cases, there may be N regions in NxN puzzle.

◆一些常见变型本质上也是额外区域，例如对角线数独或窗口数独。九阶对角线数独中，两个额外区域有一个公用的单元格。

Some other common vairant is Extra Regions essentially, such like Diagonal or Windoku. In Diagonal 9x9, the two extra regions have one cell public.

◆不同的区域图案也有特殊的名字。

These patterns own their special names:

星空(Asterisk)/烛台(Girandola)

中心(Center)/九龙(Nine Dragons)

◆三角删减 Triangle deletings

额外区域里有斜向的区块时，就会有三角删减。

Happens when slant Blocks in extra regions.

◆复杂的情况Complex cases

◆代数Unknown Covering

在这个案例中，设C3=A，额外区域内有E4=A。E4只能是4或6，但E4是6时，第四宫会没有6，所以E4=4。

Set C3=A in this example, we'll get E4=A as Hidden Singles in the Extra Region. E4 can be 4 or 6, but if A=6, no 6 will exist in Box 4, so E4=4.

练习 Practice A

① 哪一个图片展示了一个错误的额外区域？你能从另一个图里推出什么结论？

Which pic shows a wrong extra region? What inference can you get in the other one?

② 解答问号格 Find out the ？cells.

答案 Answer A

① 左图 The left; B3=C1 ② 6, 4, 6, 4 

练习 Practice B

① 例1中，额外区域里的1应该在______，C2=______。

In Practice-1, Hidden Singles of 1 in extra regions should be in ______, C2=______.

② 在例二中，哪两格相等？

In Practice-2, find the two cells with same number.

Practice 1 and 2

答案 Answer B

① D3; 2 ② A6=C5