Reverse the order of the loop vertices, effectively complementing the
region represented by the loop. For example, the loop ABCD (with edges
AB, BC, CD, DA) becomes the loop DCBA (with edges DC, CB, BA, AD).
Notice that the last edge is the same in both cases except that its
direction has been reversed.
Reverse the order of the loop vertices, effectively complementing the region represented by the loop. For example, the loop ABCD (with edges AB, BC, CD, DA) becomes the loop DCBA (with edges DC, CB, BA, AD). Notice that the last edge is the same in both cases except that its direction has been reversed.