CareerCup

step1 sorting
step2 dynamic programming + memorization

I think a for{for{}} loop is ok

psuedoocde...
We can do this as follows..
1)first sort the array.
2)Then remove the duplicate elements .
3)then taking double {for{for{}}} to make combinations

I think you don't need to sort and remove duplicates if you will use two for loops eventually.

for(i=0;i<n-1; ++i) {
    for(j=i+1; j<n; ++j){
        if (a[i] != a[j]) printf("(%d,%d) ",a[i],a[j]); 
    }
}

Let me start with an example
A = {0,2,4,5,0,1,2,3,0}
step 1 : sort it
A' = {0,0,0,1,2,2,3,4,5}
step 2 : remove duplicates along with print possible two element sets;
output will be :
sets : {0,0},{2,2}
A'' = {0,1,2,3,4,5}
now apply the simple algorithm to print all 2 element sets
for i=1:sizeof(A'')-1
for j=i+1:sizeof(A'')
output {A''[i],A''[j]}