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Free printable Bridges with answers

A bridges puzzle, also called Hashiwokakero, is a board of numbered islands you join with bridges running along the rows and columns. Each island must hold exactly its number of bridge ends, no two bridges may cross, at most two may join the same pair, and every island has to end up in one single connected network. There is nothing to add up and nothing to shade: you draw lines, and the rule that none of them may cross is what gives the puzzle its shape.

By size

More islands is what makes a board harder, not a bigger grid. A wide board with few islands gives the numbers almost nothing to choose between, so each grade adds islands and grows the board to fit them.

By audience

It has numbers on it and no arithmetic in it, and the answer is drawn rather than filled in, which makes it an easy puzzle to hand to someone who has bounced off sudoku.

One network, every time

This is the guarantee that takes real work here. The first network on a board is a spanning tree, which always pins itself. But a board whose answer is always a tree would tell you that no loop can ever close, and that is half a solve for free. So every bridge beyond that tree is added one at a time and kept only while a solver still proves the board joins up exactly one way. Adding them any other way makes most boards ambiguous: a cycle gives the numbers somewhere else to be satisfied. Every puzzle here is checked by the same solver our Publisher Studio uses. The answer prints at the back.

How to solve a bridges puzzle

Join the numbered islands with bridges running along the rows and columns, so that each island holds exactly its number of bridge ends, no two bridges cross, at most two join any pair, and every island ends up in one connected network.

The method

  1. 1Start with the islands that have no choice. Count an island’s neighbours and work out the most bridges it could possibly take: two to each. An island marked 4 with only two neighbours must send two each way. A 6 with three neighbours is the same. Those are free, and they usually open a corner.
  2. 2Use the almost-full islands next. An island marked 3 with two neighbours must send at least one bridge each way, because two to one side would leave three for the other and three is not allowed. The same reasoning gives a 5 with three neighbours one bridge in every direction. You are not placing the whole number, just the part of it that cannot go anywhere else.
  3. 3Watch what each bridge rules out. Every bridge you draw blocks the line it crosses, so a bridge between two islands can make a crossing bridge impossible and force its island to look elsewhere. That is usually where the next deduction comes from rather than from the numbers themselves.
  4. 4Never close off a group. If a handful of islands have all their numbers satisfied and no bridge joins them to the rest, the whole arrangement is wrong, because every island has to end up in one network. Checking for that as you go saves you from a board that looks finished and is not.
The one rule people get wrong
Bridges never cross, and they never pass over an island either. A line from one island to another two places away is only legal if nothing at all sits between them.
What the answer page shows
The same islands with every bridge drawn in, single or double, so you can check a pair at a glance.
How the grades differ
More islands, on a bigger board to fit them. The island count is what makes a board hard: a wide board with few islands gives the numbers almost nothing to choose between.
Is it the same as a nonogram?
No, though both work from numbers at the edge of a shape. A nonogram has you shade squares from run lengths; here you draw lines between places, and the rule that no two cross is what gives the puzzle its character.
Good for
Anyone who likes a puzzle that is drawn rather than filled in.

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