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# Bron Kerbosch Algorithm - Presentation by Jun Zhai, Tianhang Qiang and Yizhen Jia

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Bron Kerbosch Algorithm - Presentation by Jun Zhai, Tianhang Qiang and Yizhen Jia, for CS 6212 Project P4 at the GWU, Fall 2015 (Prof. Arora's class)

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### Bron Kerbosch Algorithm - Presentation by Jun Zhai, Tianhang Qiang and Yizhen Jia

1. 1. BRON-KERBOSCH (BK) ALGORITHM FOR MAXIMUM CLIQUE BY TEAM: WYD Jun Zhai Tianhang Qiang Yizhen JIa
2. 2. PROBLEM DEFINITION •  Clique: A Clique in an undirected graph G = (V,E) is a subset of the vertex set C ⊆ V, such that for every two vertices in C, there exists an edge connecting the two. •  Maximum Clique: A Clique of the largest possible size in a given graph. •  Maximal Clique: A Clique that cannot be extended by including one more adjacent vertex.
3. 3. WHY IS THIS PROBLEM IMPORTANT? •  Social Network •  BioInformation •  Computing Chemistry
4. 4. HARDNESS OF PROBLEM •  No algorithm can prove a given clique is maximum in polynomial time. •  CSAT problem can be reduced to maximum clique problem in polynomial time •  NP-HARD problem
5. 5. BronKerbosch1(R, P, X): if P and X are both empty: report R as a maximal clique for each vertex v in P: BronKerbosch1(R ⋃ {v}, P ⋂ N(v), X ⋂ N(v)) P := P {v} X := X ⋃ {v} BASIC BK ALGORITHM OUTLINE R: set of vertices that construct the Maximal Clique P: set of possible vertices may be selected X: set of vertices can not construct Maximal Clique
6. 6. BASIC BK ALGORITHM OUTLINE
7. 7. BASIC BK ALGORITHM OUTLINE
8. 8. BronKerbosch1(R, P, X): if P and X are both empty: report R as a maximal clique choose a pivot vertex u in P ⋃ X for each vertex v in P N(u): BronKerbosch1(R ⋃ {v}, P ⋂ N(v), X ⋂ N(v)) P := P {v} X := X ⋃ {v} BK ALGORITHM WITH PIVOT u: pivot vertex in P N(u): neighbor vertices of u
9. 9. BK ALGORITHM WITH PIVOT
10. 10. TIME COMPLEXITY •  Any n-vertex graph has at most 3n/3 Maximal Cliques. •  The worst-case running time of the Bron-Kerbosch algorithm (with a pivot strategy that minimizes the number of recursive calls made at each step) is O(3n/3)
11. 11. UPPER AND LOWER BOUND •  The upper bound is when the graph had the most maximal cliques. So the upper bound should be c*3n/3. •  The lower bound is when the graph is a maximal clique. So the lower bound should be c.
12. 12. REFERENCES https://en.wikipedia.org/wiki/Bron%E2%80%93Kerbosch_algorithm https://tuongphuongtn.files.wordpress.com/2012/11/baocaoseminar2012.pdf https://snap.stanford.edu/class/cs224w-readings/tomita06cliques.pdf https://www.youtube.com/watch?v=132XR-RLNoY