Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [river-crossing]

For questions regarding how to get items or people across something obeying a set of rules.

2
votes
1answer
123 views

Rigorous way to solve the river crossing problem

I encountered this classic brain teaser: Four people, A, B, C and D need to get across a river. The only way to cross the river is by an old bridge, which holds at most 2 people at a time. ...
12
votes
10answers
2k views

Another river with some extra letters

2 men are at a river. There is a boat. It holds only one person at a time. They both cross the river and continue their way... How? P.S. No Uber, helicopters, bridges, ropes, or anything else close ...
17
votes
2answers
837 views

numbers want to cross a river, but their sum must be a square number

In the world of numbers, numbers 1 to 9 want to cross a river, They have a boat which can take 1 to 3 numbers, But sum of the numbers must be a square number. The boat can not sail back itself, so ...
20
votes
7answers
3k views

Ali Baba and the 10 thieves

EDIT: This puzzle originates from the "International Mathematics Tournament of the Towns", and was published in the book "S.M.A.R.T circle overview" by Professor Andy Liu. The author has (albeit a ...
2
votes
1answer
778 views

3 cannibals and 3 missionaries on different side of the river

Three missionaries on the left side of a river and three cannibals on the right side of the river want to cross a river using a boat which can carry at most two people, The boat is on the cannibals ...
3
votes
2answers
2k views

When do missionaries and cannibals problems have solutions?

In the Missionaries and Cannibals problem: Three missionaries and three cannibals must cross a river using a boat which can carry at most two people, under the constraint that, for both banks, ...
6
votes
3answers
1k views

Zombie horde incoming! [duplicate]

Here is a puzzle I found on youtube and found quite fun to solve. You and 3 more people are for some reason running away from a horde of zombies in the darkness while holding a lantern. Suddenly, ...
7
votes
2answers
892 views

Cross the river with a small (4 spaces) boat

Giant, Slimy, Boy, Romy and Fatty want to cross a river. To cross the river there is a small boat. The boat only has 4 spaces. Every one can row the boat. At the boat, Giant needs 4 spaces. Slimy ...
6
votes
5answers
5k views

River Crossing Puzzle

There is a family which contains 4 members: Dad, Mom, Son, Daughter. They have a boat which carries only 100 kg at a time. Mom and Dad weigh 100 kg each, while Son and Daughter weigh 50 kg each. ...
8
votes
4answers
6k views

Quick!!! You got only 30 seconds

There are two checkpoints on a road namely Pt. A and Pt. B. There are 5 persons standing at the Pt. A namely P , Q , R , S, T. They have a car such that P , Q , R , S , T can travel to Pt. B in 1 , 3 ,...
-4
votes
1answer
174 views

Ancient mysteries of the Arab world [duplicate]

If we want to convey the lion and the sheep and feed from the bank of the river to the other how to do it? and the lion will not eat the sheep and the sheep will not eat the feed
-2
votes
2answers
624 views

Bridge's riddle [duplicate]

You're in a group of people going for an internship in a remote mountain lab. By mistake you pulled a lever with a skull just out of curiosity and it released some zombies. So you and your group had ...
2
votes
2answers
390 views

Crossing The River (Humans And Monsters Puzzle With A Twist)

3 couples on one side of a river. Aa Bb Cc (caps representing husbands, lowercase representing wives) One boat in which 2 people can travel at a time. At least one person must row the boat wherever ...
8
votes
2answers
689 views

Numbers nonexistent

This problem is one of the hardest problems I have ever encountered. If you don't trust links, here it is: There are some Couples wanting to cross a river by a boat. The boat can carry at most 3 ...
-1
votes
1answer
8k views

A man, a chicken, and a fox? [duplicate]

A man lives in a small house with a farm as his back garden and has a river beside his house. On the other side of the river is a shop. One day, he visited the shop, he bought a chicken and a fox for ...
6
votes
4answers
4k views

Can you solve this Bruce Wayne logic puzzle?

This variation of the classical Farmer Goat puzzle was in a puzzle contest at my college two years ago. Here it goes. Mr. Bruce Wayne is very fond of parties. Well, he’s more fond of girls, but, ...
4
votes
5answers
16k views

How can the animals get across the river without a fight breaking out?

There are three dogs and three cats that have to be transported across a river: a big dog, a medium dog and a small dog, a big cat, a medium cat, and a small cat. Rules: The raft can carry two ...
2
votes
2answers
2k views

The case of the 4 campers and the rickety bridge! [duplicate]

Four people need to cross a rickety rope bridge to get back to their camp at night. Unfortunately, they only have one flashlight and it only has enough battery left for seventeen minutes. The bridge ...
9
votes
3answers
2k views

$n$ couples crossing a river

There are $n$ couples on one side of the river. Nobody is on the other side. They have a boat that accommodates up to 2 people. For every trip across, someone(s) must bring the boat back as well. The ...
4
votes
3answers
400 views

$n$ monsters and $n$ people

There are $n$ monsters (M) and $n$ people (P) on the left side of a river. Nobody is on the right. They have a boat that can hold up to 2 beings. At no point on time may either of these be true: $$M_{...
-4
votes
1answer
2k views

How can the man get across the river with the two animals and the cabbage? [duplicate]

A man has a wolf, a goat, and a cabbage. He must cross a river with the two animals and the cabbage. There is a small rowing boat, in which he can take only one thing with him at a time. If, however, ...
-1
votes
1answer
603 views

A Fox, a Chicken, a Pile of Seeds, and a Boat [duplicate]

There's 2 islands, 1 island has a pile of seeds, a chicken, and a fox. There's also a boat next to this island, you have to get it all across with minimum uses of the boat. You can only take one ...
15
votes
1answer
5k views

Fastest way to cross a river: four people with different rowing speeds

This problem is commonly cited as a Microsoft interview problem, although I have paraphrased it here to involve a river and a boat instead of a bridge and a flashlight, and tweaked the crossing times ...
15
votes
4answers
27k views

Strategy to solve the Missionaries and Cannibals problem

In the Missionaries and Cannibals problem: Three missionaries and three cannibals must cross a river using a boat which can carry at most two people, under the constraint that, for both banks and ...
11
votes
2answers
537 views

What is the maximum number of items in a river crossing puzzle?

A River Crossing puzzle puts limits on the number of items that may cross a boundary, with limits on what may be left together. The "Fox, goose and bag of beans" is one of the earliest examples. Of ...
27
votes
4answers
16k views

Learning to Solve a River Crossing Puzzle

I have seen many variations of the following puzzle: Once upon a time, a farmer went to the market and purchased a fox, a goose, and a bag of beans. On his way home, the farmer came to the bank of ...