Saturday, September 26, 2009

[missionaries and cannibals] get them to the other side


Three missionaries and three cannibals want to get to the other side of a river. There is a small boat, which can fit only two. To prevent a tragedy, there can never be more cannibals than missionaries together.

Work out the combinations necessary to get them all safely to the other side. The solution is going to be something like:

1 missionary and 1 cannibal there, 1 missionary back;
1 missionary and 1 cannibal there .....

And so on. Solution will be given tomorrow morning.

Tomorrow morning: Answer is here.

9 comments:

Nigel Sedgwick said...

Surely you mean the boat can take 3.

Best regards

James Higham said...

You always catch me out, Nigel.

Nigel Sedgwick said...

I'm sure I've done this before, years ago. Anyway, I have a newly calculated solution; that is with 3 people allowed in the boat.

I don't think it can be done with just a 2-person boat, but I will look a little while longer for a solution, or proof that there is no path through the graph.

Best regards

ScotsToryB said...

2 cs cross
1 returns.

1c+1m crosses
1m returns
1m+1c crosses
1m returns

2ms cross
1 returns
2ms cross.

Everybody is cross in this tale.

STB.

James Higham said...

Yes 2 cs cross
Yes 1 returns.

Yes 1c+1m crosses
Yes 1m returns

Yes 1m+1c crosses
Yes 1m returns

Yes 2ms cross
No 1 returns

2ms cross.

That would leave the missionary outnumbered.

James Higham said...

Nigel - the boat's for two.

Lord T said...

ScotsToryB said...
2 cs cross
1 returns.

1c+1m crosses

Delivery service to 2c's of 1m at far side. Yummy.

btw: Why is it a tragedy that the poor misunderstood black cannibals are fed by the oppressive missionaries.

Trip 1 MC
Return M
Trip 2 CC
Return C
Trip 3 MM
Return MC
Trip 4 MM
Return C
Trip 5 CC
Return C
Trip 6 CC
All done. Cannibals hungry.

Nigel Sedgwick said...

http://en.wikipedia.org/wiki/Missionaries_and_cannibals_problem

And congrats to Lord T.

Best regards

James Higham said...

Thanks all - the "official answer" has been up all along here.

Congrats!

[No women took part - hmmmm.]