Reading Ship Pieces: What Ends, Middles and Submarines Tell You

In a Battleship puzzle, a revealed square shows water, a submarine, an end piece or a middle piece, and each one forces specific squares around it. A submarine makes all eight neighbours water. An end piece makes one neighbour a ship square and the other seven water. A middle piece makes its four corners water and leaves only two ways for the ship to run. Read every revealed piece this way before you touch the counts.

This guide is for players who know the rules of Battleship solitaire and want to get more out of the squares a puzzle gives away. If the rules are new to you, start with how to play Battleship solitaire. Squares are named by row and column from the top left, so R2C3 is row 2, column 3.

The four kinds of revealed square

A Battleship solitaire puzzle may start with some squares already solved, and each one is drawn as a shape: water, a submarine, the end of a ship or the middle of a ship. That is the classic way the clues are shown, as described in the Wikipedia article on the puzzle). In the diagrams below, the pieces are written like this:

All four rest on the same two rules: ships are straight lines, and ships never touch, not even at a corner. If the no-touch rule is not second nature yet, our guide to why ships never touch explains the diagonal rule that every piece below relies on.

Submarines: the whole ship in one square

A revealed submarine is the easiest piece to read: it is a complete ship, so every square around it is water. In open water that is eight squares, on an edge five, in a corner three.

	o

Then cross it off. Each submarine you find is one fewer to place, and on Easy there are only three. When the last submarine is placed, any lone ship square you find later must be part of a longer ship, which tells you it has at least one ship neighbour.

End pieces: one ship square forced, seven water

An end piece tells you more than it seems to. The square on its flat side, the way the ship runs, is a ship square. All seven other neighbours are water: the square behind it is past the end, the two beside it would bend the ship, and the four corners are water by the no-touch rule.

	<

Look at what that one piece decided: one ship square and nine water squares in a 3x4 patch. The only open question is the length. The ship is at least two long, and the square after the forced one (R2C4 here) is either more ship or the water that ends it.

Three situations settle the length quickly:

• The edge is one square away. A left end in the second-to-last column must be a ship of two: the forced square sits against the edge. That ship is complete, so its whole ring is water.
• The count is tight. A top end in a column whose count is 2 must be a ship of two: the end and its forced square already fill the count.
• Water is revealed two squares along. A top end in R1C2 and revealed water in R3C2 leave room for just R2C2, so again the ship is a destroyer, complete, with water all round.

	^

Middle pieces: which way does the ship run?

A middle piece is a square inside a ship of three or four, so it always has ship squares on two opposite sides. Its four corners are water at once. The four side squares are the question: either the left and right squares are ship and the top and bottom are water, or the other way round.

Four things decide the direction, and one of them usually applies:

1. An edge. A middle piece on the top or bottom row cannot run vertically, because there is no square on one side. It runs along the edge. The same holds for the left and right columns. That is also why you will never see a middle piece in a corner.
2. A water square beside it. If any one of its four side squares is known water, the ship runs the other way.
3. A low count. A middle piece running across a row puts at least three ship squares in that row. So if the row's count is 1 or 2, the ship runs down the column instead. The same test works on the column.
4. No room. If one direction has no space for a ship of three without touching a known ship, the other direction wins.

The ends of a middle piece's ship are open until you know its length. On Easy that is never in doubt, as the next sections show.

What the fleet tells you about pieces

The fleet decides which pieces can exist at all. A middle piece only appears in a ship of three (one middle) or a ship of four (two middles). End pieces come two to a ship of two or longer. Submarines are their own ships. Here is the full count for each level of Puzzle Picnic's Ships:

The Easy row is the useful one to remember. The Easy fleet has a single ship of three and no ship of four, so it has exactly one middle piece. If you see a middle piece on Easy, it is the centre of the ship of three, and as soon as you know its direction you know the whole ship and can draw water all round it.

On Medium and up, a middle piece could be the centre of a cruiser or one of the battleship's two middles. Two middle pieces side by side are always the battleship's two middles, because a cruiser has only one. That fixes all four squares of the battleship at once. Our Battleship solitaire strategy guide goes further into this kind of fleet accounting.

Two pieces in the same line

Two revealed pieces in one row or column often fix a ship's length exactly. The most common case is two ends facing each other.

<

>

The logic: the left end forces C3, the right end forces C4, and C3 and C4 touch. Touching ship squares cannot belong to different ships, so the whole run from C2 to C5 is one ship, four long. With one square between the ends instead, the ship is a cruiser of three.

Other useful pairs:

• An end and a middle in line. A left end in C2 with a middle in C4 makes C3 a ship square. The middle now has ship on its left, so it runs across and C5 is a ship square too. That is four squares from C2 to C5: the battleship, complete, with water in C6. It is tempting to read C2 to C4 as a cruiser, so read both pieces fully before you cap anything.
• An end and revealed water. As in the earlier diagram, the gap between them is the most room the ship has.
• Two ends pointing away from each other. A right end in C3 and a left end in C4 are two different ships, side by side, which the rules forbid. You will not see this in a fair puzzle, but it is a good check that you have read the symbols the right way round.

A worked 6x6 with a middle and a submarine

Here is a complete Easy-sized puzzle solved by reading its two revealed pieces first. The fleet is one ship of three, two ships of two and three submarines.

			o

Step 1: the zero row. Row 6 has a count of 0, so it is all water.

Step 2: the middle piece. R1C4 is on the top edge, so its ship runs across: R1C3 and R1C5 are ship squares. On Easy the only ship with a middle is the ship of three, so this ship is exactly R1C3 to R1C5, and it is complete. Its ring is water: R1C2, R1C6 and R2C2 to R2C6. Row 1 now has its three ship squares, so R1C1 is water too.

Step 3: the submarine. Everything around R3C4 is water: R3C3, R3C5 and R4C3 to R4C5 are new.

			o

Step 4: row 2 and column 1. Row 2 needs one ship square and R2C1 is its only open square, so it is a ship. Column 1 needs only one, so R3C1, R4C1 and R5C1 are water. R2C1 now has water above, below and to its right: it is a submarine, and its corner R3C2 is water.

Step 5: row 3. Row 3 needs one ship square and already has the revealed submarine, so R3C6 is water.

Step 6: column 4. Column 4 needs three. It has R1C4 and R3C4, and its only open square is R5C4, so that is the third. Columns 3 and 5 each need one and already have it in row 1, so R5C3 and R5C5 are water. R5C4 has water on all four sides: another submarine, the third and last.

Step 7: rows 4 and 5. Row 4 needs two, and its only open squares are R4C2 and R4C6. Row 5 needs three: R5C4 and its open squares R5C2 and R5C6. All four are ships, and they form two vertical ships of two, in column 2 and column 6. The fleet is complete.

			o

The two revealed pieces did most of the early work. The middle piece alone placed a whole ship and its ring of seven water squares, and the submarine's ring added five more. After that, every step was a simple count.

Frequently asked questions

What does a middle piece mean in a Battleship puzzle?

A middle piece is an inner square of a ship of three or four. It has ship squares on two opposite sides, either left and right or above and below, and water on all four corners. An edge, a neighbouring water square or a low row or column count tells you which way it runs.

Which way does an end piece point?

An end piece is rounded or pointed on the outside and flat on the side where the ship continues. The square against the flat side is always a ship square. In this guide, < is a left end with the ship running right, and ^ is a top end with the ship running down.

Can a revealed square be wrong or misleading?

No. In a fair Battleship puzzle every revealed square is part of the one solution, so you can build on it with full confidence. In Puzzle Picnic every puzzle has exactly one solution and can be solved by logic alone, without guessing.

Do all Battleship puzzles reveal squares?

Not always. Harder puzzles reveal fewer squares, and some reveal none, leaving only the counts and the fleet. In Puzzle Picnic's Ships, Easy reveals a few squares to start and Expert usually reveals none.

Where to go next

Make reading the revealed squares your first step in every puzzle, before any count: submarines and their rings, ends and their forced square, middles and their direction. Then use the counts on what is left. If you want to see how the counts and the fleet work together from there, the Battleship solitaire strategy guide is the next read, and our post on easy to expert puzzle levels explains what changes as the grids grow.

To practise, open the Ships page, which has the rules and a Play button. Easy reveals a few squares to start, so it is the best place to train your eye.

Sources

• Wikipedia: Battleship (puzzle))
• Conceptis Puzzles: Battleships techniques