Nonogram Technique: Cross Out Finished Lines
Crosses look like bookkeeping, but they carry information: a cross in one line is a known empty cell in the line that crosses it. This lesson uses a 7×7 picture, an arrow, with its full row and full column already filled, and the overlaps of rows 3 and 5.
Step 1 of 4
A finished line
Row 1's clue is 1, and the filled cell in column 4 is that 1. The line is finished: the board strikes its clue through, and every other cell in it, starred here, is empty. Row 7 is finished too, and so is every column whose clue is struck through.
Cross it out
Rows 1 and 7 are crossed out now. Look at column 7: its clue is 1, and its 1 is the filled cell in row 4. That column is finished too.
Your move
Cross out the four blank cells of column 7.
The crosses pay off
Row 3's clue is 6, in seven cells. Until now the block could be columns 1 to 6 or 2 to 7, so the overlap left column 1 unknown. Column 7 is crossed out now, so the 6 has exactly six cells left, and column 1 is filled. Row 5 is the same.
Your move
Fill the cells the new crosses prove in rows 3 and 5.
What's left in row 2
Columns 1 to 3 are finished now, and crossed out. Row 2's clue is 2, and its fourth cell is filled. Which other cell is filled?
What you learned
- A line is finished when its filled cells match its whole clue. Every other cell in it is empty.
- Cross those cells out. A cross is a known empty cell for the line running across it.
- A cross can turn an overlap into a whole block, or give a block a wall to push against.
In this course
Unit 1The rules
Unit 2Solving techniques
- Nonogram Overlap Technique (Simple Boxes)
- Nonogram Edge Technique: Start From the Wall
- Nonogram Technique: Cross Out Finished Lines
- Nonogram Joining and Splitting Techniques
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