Tips for Finding Hidden Singles
A Hidden Single is when a particular number can only go in one cell within a row, column, or block. While Naked Singles look at cells, Hidden Singles require you to think from the number's perspective. They are harder to spot at first, but your eye will learn with practice.
Basic Search Method
Step 1: Pick a Number and Scan
Focus on "1" first. Look across the entire board, visualizing "elimination lines" from each existing 1.
Step 2: Find Candidates in Each Block
Within each 3×3 block, find empty cells not blocked by elimination lines. If only one cell remains, that is a Hidden Single.
Step 3: Repeat for 1 Through 9
After checking 1, move to 2, 3, and so on. Nine scans total. With practice, each scan takes about 10 seconds.
Common Stumbling Blocks
❌ Only thinking by cell, not by number
→ Hidden Singles require a "number perspective." Practice consciously switching your viewpoint.
❌ Missing cross-block eliminations
→ Elimination from rows and columns affects cells across block boundaries. Think beyond blocks.
❌ Over-relying on pencil marks
→ Pencil marks are helpful, but first practice finding Hidden Singles by sight. You will see the board better.