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CS Unplugged activity

Solo Battleship

About 20 minutesSoloPencil

A fleet of ships is hiding on the grid, but you can’t see them. The numbers next to each row and column tell you how many squares in that row or column are ships, and that’s all you need. No guessing: every square you shade should follow from a number you can already see.

Try a small one first

Here is a 4 by 4 grid with a fleet of one 2-ship and two 1-ships. One square is already shaded for you.

	2	1	0	1
1
1
1
1

Start: one given ship square, column 3's count is 0.

1. Column 3 has a count of 0. That means every square in column 3 is water, right away, no thinking required.
2. The shaded square is in row 2. Ships never touch, not even at a corner, so the two squares diagonally touching it are water too.
3. Row 2 already has its one ship square. Its count is 1, and that square already found it, so the rest of row 2 is water as well.

Working the same way through every row and column finishes the grid:

	2	1	0	1
1		•	•	•
1		•	•	•
1	•	•	•
1	•		•	•

Finished: a 2-ship in column 1, and two 1-ships.

The puzzles

The fleet list is printed next to each grid so you can cross off a ship the moment you find it.