Problem 487. Find perfect placement of non-rotating dominoes (easier)

Given a list of ordered pairs, find the order they should be placed in a line, such that the sum of the absolute values of the differences is zero.

list = [1 2
        4 3
        2 4

order = [1 3 2]

yields: [1 2][2 4][4 3]
    or: abs(2-2) + abs(4-4)
    or:        0 + 0
    or: 0

There is a unique solution to this problem where the final score is zero.