River Crossing Puzzle Online
Get everyone across without breaking the rules. Five classic puzzles, each with hints and the shortest solution.
How to use the River Crossing Puzzle
- Choose a variant from the chips at the top: Wolf, goat & cabbage, Missionaries & cannibals, Jealous husbands, Bridge & torch, or Family crossing.
- Adjust the settings if you want a harder version. For missionaries and cannibals, pick 2 to 6 of each and a boat size of 2 to 4. For bridge and torch, pick 3 to 6 people, set their walking times from 1 to 99 minutes, and set a time limit.
- Tap a character to put them in the boat. Tap again to take them out.
- Tap Cross to make one trip. A crossing is one trip from one bank to the other, so a round trip counts as two.
- If a move breaks a rule, the tool names the rule and cancels that crossing. Read the message, then try a different move.
- Use Undo to step back one move, or Reset to start the puzzle again.
- Tap Hint to see the next good move from your current position.
- Watch the crossings counter (and minutes, for bridge and torch) and compare it with the theoretical minimum shown on the page.
- Tap Show solution to play a shortest solution step by step with Previous and Next. Tap Back to my game to return to your own position.
How do you solve the wolf, goat and cabbage puzzle?
The shortest solution takes 7 crossings, and the goat goes first. The farmer can leave the wolf with the cabbage, but never the wolf with the goat or the goat with the cabbage, so the goat must be moved in a way that keeps it safe.
The order is: take the goat over, return alone, take the wolf over, bring the goat back, take the cabbage over, return alone, then take the goat over. The goat is carried back once, which is why the count is 7 and not 5.
What is the bridge and torch puzzle answer for 1, 2, 5 and 10 minutes in 17?
The minimum time is 17 minutes. The two slowest people should cross together, so their long walking times overlap instead of adding up, and the fastest person should bring the torch back.
The sequence is: 1 and 2 cross (2 minutes), 1 returns with the torch (1 minute), 5 and 10 cross (10 minutes), 2 returns with the torch (2 minutes), then 1 and 2 cross again (2 minutes). The total is 17. Other groups give other minimums: 1, 2, 5 and 8 take 15 minutes, and 1, 3, 4 and 5 take 14.
What is the jealous husbands puzzle?
The jealous husbands puzzle is a crossing puzzle with several married couples. The rule is that no wife may be with another man, on a bank or in the boat, unless her husband is also present.
The default is 3 couples with a boat of 2, which takes 11 crossings. With 2 couples the minimum is 5 crossings. Four or more couples need a boat that holds 3. With a boat of 3, 4 couples can be solved in 9 crossings.
What is the family river crossing puzzle with the police officer and thief?
It is a crossing puzzle for a family of six plus two outsiders: a father, mother, two sons, two daughters, a police officer and a thief. It is also called the river crossing puzzle with a prisoner, because the thief is the one who must be guarded.
The raft holds 2 people, and only the father, the mother and the officer can row. The father cannot be with a daughter without the mother, the mother cannot be with a son without the father, and the thief cannot be with any family member without the officer. These rules apply on both banks and on the raft. The minimum is 17 crossings.
Frequently asked questions
Is the river crossing puzzle free?
Yes. The tool is free, runs in your browser, and does not require an account or sign-up. Nothing is uploaded.
Does it work on a phone or tablet?
It works on a phone. On a phone the river is drawn vertically so everything fits on the screen.
What does one crossing mean?
A crossing is one trip from one bank to the other. A trip there and back counts as 2 crossings.
What if a missionaries and cannibals setting has no solution?
Not every setting can be solved. For example, with a boat of 2, 4 missionaries and 4 cannibals is impossible. The tool tells you when a setting has no solution.
Why is the bridge and torch answer 17 and not 19?
Sending the fastest person back every time gives 19 minutes (2 + 1 + 5 + 1 + 10). The 17-minute answer sends the two slowest people over together, so the 10-minute walk also covers the 5-minute walker, and the 2-minute person brings the torch back once.
Can I see the answer to a puzzle?
Yes. Show solution plays a shortest solution step by step. Use Previous and Next to move through it, and Back to my game to return to your own position.
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