Problem 45218. Find a common edge

First input is T, a triplet list of indices. Second input is e = [e1 e2], a row vector, couple of indices (positive distinct integers always sorted in ascending order, ie e1 < e2 ). The goal of this function is to find and return the indices of the rows in the list which contain this particular edge. Output format can be either a column or a row vector.
For example if inputs are
T = [1 2 3 ;
1 3 4 ;
1 4 2 ;
2 3 4]
and
e = [2 3]
the output is the vector
row_idx = [1 4]
since [2 3] is contained in rows number 1 and 4 of T. With the same input T, but with e = [2 4] this time, the output is the vector row_idx = [3 4], since [2 4] is contained in rows number 3 and 4 of T (Note that edge [b a] is the same as edge [a b] so must be the corresponding outputs). If the edge is not in the list, the function must of course return the empty set.
See also
Solve

Solution Stats

58.82% Correct | 41.18% Incorrect
Last Solution submitted on Dec 21, 2025

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