Problem 45259. Build edges list

Input T is a triangulation connectivity indices list (triplet list of indices -positive integers-, each index refering to a vertex number in a corresponding vertices list).

The purpose of this function is to query the list E of all the edges.

For instance if T = [1, 2, 3; 4, 5, 6; 7, 8, 9], then the output of the function must be E = [1, 2; 1, 3; 2, 3; 4, 5; 4, 6; 5, 6; 7, 8; 7, 9; 8, 9] (all the 3 possible combination of the 3 vertices of a triangle / row, for every triangle / row of the list).

Hypothesis on output E :

• size(E) = [N, 2], with N the number of edges
• E doesn't need to be ordered neither following dimension 1 (rows) nor dimension 2 (columns), but must not contain duplicated edges
• Edges are symmetric : [e1, e2] is the same edge as [e2, e1]
• Every indices are positive, distinct integers.