The clique problem on inductive $k$-independent graphs

TL;DR

This paper introduces approximation and fixed parameter tractability algorithms for the maximum clique problem on inductive $k$-independent graphs, and improves algorithms for $k$-degenerate graphs, with structural insights.

Contribution

It presents a polynomial-time approximation algorithm for maximum clique on inductive $k$-independent graphs and shows fixed parameter tractability, also improving algorithms for $k$-degenerate graphs.

Findings

Approximation ratio of $ar{ riangle} / log(log(ar{ riangle}) / k)$ for maximum clique.

Fixed parameter tractability with complexity $O(1.2127^{(p+k-1)^k} n)$.

Improved maximum clique algorithm for $k$-degenerate graphs with time $O(1.2127^k (n-k+1))$.

Abstract

A graph is inductive $k$-independent if there exists and ordering of its vertices $v_{1},...,v_{n}$ such that $\alpha(G[N(v_{i})\cap V_{i}])\leq k $ where $N(v_{i})$ is the neighborhood of $v_{i}$, $V_{i}=\{v_{i},...,v_{n}\}$ and $\alpha$ is the independence number. In this article, by answering to a question of [Y.Ye, A.Borodin, Elimination graphs, ACM Trans. Algorithms 8 (2) (2012) 14:1-14:23], we design a polynomial time approximation algorithm with ratio {$\overline{\Delta} \slash log(log(\overline{ \Delta}) \slash k)$ for the maximum clique and also show that the decision version of this problem is fixed parameter tractable for this particular family of graphs with complexity $O(1.2127^{(p+k-1)^{k}}n)$. Then we study a subclass of inductive $k$-independent graphs, namely $k$-degenerate graphs. A graph is $k$-degenerate if there exists an ordering of its vertices $v_{1},...,v_{n}$ such that $|N(v_{i})\cap V_{i}|\leq k $. Our contribution is an algorithm computing a maximum clique for this class of graphs in time $O(1.2127^{k}(n-k+1))$, thus improving previous best results. We also prove some structural properties for inductive $k$-independent graphs.