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Skyscrapers: One Place Left

When a height can only go in one square of a row or column, it goes there, even if that square could still be other heights.

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This is one of the Skyscrapers techniques. Each page shows its technique on the same 7×7 from the game, Hard level 1.

The rule

  1. Pick a row or column, and a height it still needs.
  2. For each empty square in it, ask: could this height go here? Not if the square’s other line already has it, and not if the notes or clues rule it out.
  3. If only one square is left, the height goes there.

In a real puzzle

On the 7×7, it’s first needed at step 8. Row 6 still needs its 7, and only one square in it can still take one.

Step 8: one place left in row 6 Row 6 has only one square left that could take its 7. 7 5 2 7 3 7 7 1 5 7 3 7 1 3 3 4 1 2 2 3 4 3 4 3 3 2 3
Step 8: row 6 has one place left for its 7.

How often you’ll need it

On 43 of the 50 Easy levels, 49 Medium and every Hard one: 2.6 times per Easy level on average, 4.1 on Medium and 7.2 on Hard. It’s 9 of the 47 moves on the 7×7 here.

Next steps

Questions

Which height should I look for?

The tallest is a good start: clues often rule it out of all but one square in a line. But any height a line still needs can have one place left.