Hashi Solver, Step by Step
Tap a square to make it an island and tap again to raise its number, up to 8; once more clears it. On a keyboard, type the number, or Delete to clear.
How to use the hashi solver
Set the width and height, then put each island in its square with its number. Press Explain the next step: the solver draws the bridges that are certain, crosses out ones that cannot be, highlights what changed, and says why. Show the answer draws them all at once and checks the solution is the only one. The puzzle is also called bridges, or hashiwokakero.
The rules of hashi
Each circle is an island, and its number is how many bridges end there. Bridges run straight across or down between two islands, at most two between any pair, and they never cross each other or pass over an island. When the puzzle is done, every island can be reached from every other by bridges.
How to solve hashi, step by step
Count what each island's neighbours can take. An island needs its number of bridges, and each neighbour can take at most two from it, or fewer if its own number is small. When the neighbours together can only just cover the number, every bridge is certain: a 4 with two neighbours, a 6 with three, an 8 with four. When they can cover all but one or two, each neighbour still gets at least one. Don't cut an island off. Two 1s next to each other cannot be joined, because the pair would have nowhere else to go; the same holds for a 2 and a 2 and any group that would close itself off. When those run out, the solver tries a bridge both ways and keeps the one that does not break a rule.
How it was checked
The solver was run on all 120 puzzles of the daily hashi, and its count of answers was checked against a separate brute-force search for every one. Every step it explained was checked against the answer: it never drew or ruled out a bridge wrongly. It was also run on 30 larger boards, up to 15 by 15.
More logic puzzles
There is a new daily hashi every day. The numberlink solver joins dots with lines, and the nurikabe solver explains its steps the same way. For a puzzle you hold in your hands, see our brain teasers. There are more solvers on the puzzle tools page.
Frequently Asked Questions
How do you solve hashi?
Count what each island's neighbours can take. When they can only just cover its number, every bridge is certain: a 4 with two neighbours or a 6 with three. When they can cover all but one or two, each neighbour still gets at least one bridge. Never join a group that would close itself off, such as two 1s.
What are the rules of hashi?
Each island's number is how many bridges end there. Bridges run straight between two islands, at most two between any pair, never crossing each other or passing over an island, and all the islands end up connected.
Is hashi the same as bridges?
Yes. Hashiwokakero, often shortened to hashi, is the Japanese name; in English it is usually called Bridges.
Can two 1s be joined in hashi?
No, unless they are the only two islands in the puzzle. Joined, both are finished, so the pair is cut off from every other island, and every island has to connect.
Does every hashi have one solution?
A well-made one does. The solver counts, and says if the islands you entered allow more than one.