You have already done everything, where r u stuck...about that swap logic?

well here is how it works,

suppose you have oil on bucket A

A=oil

 and water in bucket B

B=water

, now you got to transfer oil to B and water to A,

final result B=oil, A=water

 how will you do it?

Take another empty bucket C.

Put oil from A to C

C=A; (well in  real world bucket A will get empty, but in programming,  A and C both will have oil, ignore  that and think this is real world)

Then,

Put the content of B(water) to A, so A contains water

A=B;

then put the content of C(oil)  to B, so B contains Oil

B=C

This is how swap works.

For your problem

temp=list(i);

list(i)=list(i+1);

list(i+1)=temp;

Hope that explains .

 Post your code, if therez logical or syntax error we can point it out. Java or C or C++?