Problem 45230. Remove duplicated triangles

Input T is a triangulation (triplet list of indices -positive integers-, each index refering to a vertex number in a corresponding vertices list).
It sometimes happens a triangle may be duplicated several times. The goal of this problem is to remove all the duplicated triangles of T, and to keep only one.
For instance if :
T_in = [1 2 3;...
4 5 6;...
1 2 3;...
7 8 9;...
6 4 5;...
10 11 12;...
2 1 3;...
8 7 9;...
10 11 12]
then the output must be :
T_out = [1 2 3;...
4 5 6;...
7 8 9;...
10 11 12]
since rows [1 2 3], [6 4 5], [2 1 3], [8 7 9], and [10 11 12] are just duplicata. Indeed triangle [i2 i1 i3] is the same as triangle [i1 i2 i3] for example.
Hypothesis :
  • T is always a N x 3 integer matrix with N > 0 (non empty matrix)
  • Each row / triangle of T always contains three distinct integers
See also
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Solution Stats

55.86% Correct | 44.14% Incorrect
Last Solution submitted on Nov 16, 2025

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