Clément Legrand – Duchesne

I am a second year PhD student at LaBRI in Bordeaux. You might be looking for Clément Legrand – Lixon who studied at ENS Rennes at the same time as me.

I study graph theory and I am mainly working on coloring reconfiguration under Kempe changes. My supervisors are Marthe Bonamy and Vincent Delecroix and I am member of the teams Graphes et Optimisations and Combinatoire et Interactions.

Academic Background

Second year of Master's Degree in computer science

2020 - 2021

Training for the "Agrégation" of mathematics (computer science option)

The agrégation is a competitive exam to become a teacher in high school or in classe préparatoire or university. The goal of this intense preparation is to review my knowledge in mathematics. At the end of it, we are expected to be able to teach maths until the first year of master's degree.
Successful and ranked 217 among 3200 candidates.
2019 - 2020

Bachelor and first year of Master's Degree in computer science

2017 - 2019


Two years of intensive mathematics, physics and computer science in order to join the ENS.
2015 - 2017

Publications, conferences and Workshops


  • Recoloring version of Hadwiger's conjecture, arXiv:2103.10684, with Marthe Bonamy, Marc Heinrich and Jonathan Narboni. Submitted to JCTb.
  • Kempe changes in bounded treewidth graphs, EuroComb 2021, to appear, with Marthe Bonamy and Vincent Delecroix.
  • Parameterized complexity of untangling knots, arXiv:2111.05001, with Ashutosh Rai and Martin Tancer.
  • Kempe changes in degenerate graphs, arXiv:2112.02313, with Marthe Bonamy and Vincent Delecroix. Submitted to European Journal of Combinatorics.
  • Strengthening a theorem of Meyniel, arXiv:2201.07595, with Quentin Deschamps, Carl Feghali, František Kardoš and Théo Pierron.

Workshops and contributed talks

  • Journées ANR GrR (June 2021)
  • Kempe changes on \(\Delta\)-colorings: Workshop on Combinatorial Reconfiguration at ICALP 2021
  • Sparse Graph Coalition Workshop on Reconfiguration (May 2021)
  • Kempe changes in bounded treewidth graphs: Eurocomb 2021
  • Recoloring version of Hadwiger's conjecture:
    • Bordeaux Graph seminar (October 15, 2021)
    • JGA 2021 (November 18, 2021)
    • LSE combinatorics seminar (December 3, 2021)
    • Oxford combinatorial theory seminar (February 1, 2022)
  • Strengthening a theorem of Meyniel:
    • Journées ANR GrR (June 2022)
    • JGA 2022
    • Bordeaux Graph seminar (November 25, 2022)
  • Parametrized complexity of untangling knots:
    • ICALP 2022
    • LaBRI's Junior seminar (October 26, 2022)



When I'm not working, I enjoy doing sports. I practise bouldering, ultimate-frisbee and cross-country unicycle several times a week.

I am also a big ski and snowboard enthusiast, and love surfing or going for a ride on my longboard in summer.

When the weather isn't good enough for those activities, I like to read (mainly Sci-fi and Heroic Fantasy), to listen to music or to play classic guitar. I am also a big fan of cooking.