# Find the adjacent tetrahedron of a specific tetrahedron by vertex e?

**URL:** https://community.freefem.org/t/find-the-adjacent-tetrahedron-of-a-specific-tetrahedron-by-vertex-e/4115
**Category:** General Discussion
**Created:** [October 27, 2025, 1:38am UTC](https://community.freefem.org/t/find-the-adjacent-tetrahedron-of-a-specific-tetrahedron-by-vertex-e/4115 "2025-10-27T01:38:06Z")
**Posts on this page:** 1
**Showing post:** 3

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### Author: ![MatrixVector](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@MatrixVector](https://community.freefem.org/u/MatrixVector)
#### Post date: [November 3, 2025, 11:40am UTC](https://community.freefem.org/t/find-the-adjacent-tetrahedron-of-a-specific-tetrahedron-by-vertex-e/4115/3 "2025-11-03T11:40:44Z")

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Dear Dr. Bouchut,

Thanks for your reply. Regarding that “finding the tetrahedra with a common vertex“, maybe the way using lists proposed by Prof. Hecht works better.

> [@Mesh connectivity details](https://community.freefem.org/t/mesh-connectivity-details/1285/2):
>
> You want for each vertices of the mesh the list of triangle contening this vertex: // you can do that in few line of code: mesh Th=square(4,4); int[int] headv(Th.nv), next(Th.nt\*3); headv=-1; // for(int k =0;k\< Th.nt; ++k) for(int i =0;i\< 3; ++i) { int v = Th[k][i]; // vertex number next[3k+i] = headv[v]; headv[v]= 3k+i; } // show the list of triangle of vertex v for(int v=0; v\<Th.nv;++v) { cout \<\< v \<\< " : "; for(int p=headv[v]; p \>=0; p=next[p]) { int k = p/3, i = p%3; ass…

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