RocketSudoku.com

Skyscraper

Hard

Parallel StrongLinks on one digit leave two RoofCells; anything that sees both loses that digit.

How it works

6
5
9
1
1
1
7
2
8
7
4
9
6
1
3
4
1
7
6
9
2
5
2
7
4
4
8
1
7
1
1
7
6
4
9
3
8
8
1
3
9
5
4
7
2
6
9
2
5
6
8
7
3
7
6
4
1
2
3
8

Locate the first wall

Start with any column or row with a between two cells.

6
5
9
1
1
1
7
2
8
7
4
9
6
1
3
4
1
7
6
9
2
5
2
7
4
4
8
1
7
1
1
7
6
4
9
3
8
8
1
3
9
5
4
7
2
6
9
2
5
6
8
7
3
7
6
4
1
2
3
8

Locate the second wall

Find a parallel column or row with a between the same two cells on the same digit.

6
5
9
1
1
1
7
2
8
7
4
9
6
1
3
4
1
7
6
9
2
5
2
7
4
4
8
1
7
1
1
7
6
4
9
3
8
8
1
3
9
5
4
7
2
6
9
2
5
6
8
7
3
7
6
4
1
2
3
8

Do they connect?

The wallls must share a single row or column. These cells make up the "floor" of the Skyscraper.

6
5
9
1
1
1
7
2
8
7
4
9
6
1
3
4
1
7
6
9
2
5
2
7
4
4
8
1
7
1
1
7
6
4
9
3
8
8
1
3
9
5
4
7
2
6
9
2
5
6
8
7
3
7
6
4
1
2
3
8

Spot the contradiction

If neither roof cell is 1, the floor row would have two 1's and be invalid.

6
5
9
1
1
1
7
2
8
7
4
9
6
1
3
4
1
7
6
9
2
5
2
7
4
4
8
1
7
1
1
7
6
4
9
3
8
8
1
3
9
5
4
7
2
6
9
2
5
6
8
7
3
7
6
4
1
2
3
8

One roof cell must be 1

So one of these roof cells is certain to be 1.

6
5
9
1
1
1
7
2
8
7
4
9
6
1
3
4
1
7
6
9
2
5
2
7
4
4
8
1
7
1
1
7
6
4
9
3
8
8
1
3
9
5
4
7
2
6
9
2
5
6
8
7
3
7
6
4
1
2
3
8

Eliminate shared peers

Safely remove 1 from any cell that sees both roof cells.

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the Skyscraper on your board.

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Two String KiteHard