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Hidden Single

Hidden SingleSTEP 0/2

Introduction to strategy

The next technique is Hidden Single. We look for a situation where a given digit within the entire row, column or block fits:

Only and exclusively in one, specific place
Although other digits could theoretically stand in this field

This digit is "hidden" because at first glance the field seems to have many options.

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Hidden SingleSTEP 1/2

Position blocking

Look at the highlighted cell. We want to place a specific digit in it. See how neighboring rows and columns affect this block:

The same digits in adjacent lines "cut off" entire rows or columns in this block
Most free fields in the block are blocked in this way

Note that for our sought digit, only one free path remains.

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Hidden SingleSTEP 2/2

Entering a digit

Analyze the fields blocked by adjacent lines:

Notice which single field in the block resisted the line blockades
This means that this specific digit must go right there

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