WATER BUCKETS

In lethal weapon (I think some movie or other that I haven't seen anyway) some people were asked to get a certain amount of water in one bucket based on two other ones Bucket A and Bucket B which hold in 5 and 7 litres each. I think they were asked (this was to save their lives) to get exactly 3 litres in Bucket B using only these three operations

Fill - completely fill container A

Empty - completely empty container B

Transfer - Transfer contents from A to B untill B is Full or A is empty

this task sounds very hard lets look at a trial set of steps

command

Step	Operation	# of litres in A	# litres in B
1	Empty	?	0
2	Fill	5	0
3	Transfer	0	5
4	Fill	5	5
5	Transfer	3	7
6	Empty	3	0
7	Transfer	0	3

this is pretty good but can we do it for other amounts?

The answer is yes, It turns out that any amount between 0 and 7 litres can be placed in bucket B you just have to break it down into smaller operations.

(i) If  Bucket A is Empty (or unknown) fill it

(ii) If Bucket B is Full empty it

(iii) If Bucket B is not Full or Bucket A is not empty then Transfer

You can see this makes it a lot simpler. I wrote a c++ program that demonstrates this you can download it here.

waterbuckets.cc -The code

waterbuckets.zip - The code and the executatble