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Last Possible Number

Last Possible NumberSTEP 0/2

Introduction to strategy

Time for the Naked Single strategy. We use it when we look at one specific field and check what digits can jump into it at all:

You analyze the row, column and block crossing this field
You list all the digits that are already blocked

If after rejecting the blocked digits you are left with only one option

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Last Possible NumberSTEP 1/2

Scanning constraints

Look at the cell that the game has just highlighted on the board. See how many digits restrict it from different sides:

There are already several unique digits in its row and column
There are also other numbers in its 3x3 block

All these visible digits "cross" on this one field and eliminate themselves.

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Last Possible NumberSTEP 2/2

Elimination and entry

Gather in mind all digits visible in the highlighted row, column, and block.

Discard digits from 1 to 9 that already appear there
Notice that for this cell, only one single possibility remains. Digit 1

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