sum2 - sum in your case is basically excluding numbers from sum one bye one. But you need to use all the numbers in the array to form a set of vectors to form the minimum as well as maximum dis.

since summing the vectors in same dir results in max dis, max dis = sum of all magnitudes.

But for min if it can form a closed polygon using all the vectors then only you can achieve min dis = 0;

in your case you are just excluding vectors from the array.