, Volume 43, Issue 2, pp 402-411

Untangling Polygons and Graphs

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Abstract

Untangling is a process in which some vertices in a drawing of a planar graph are moved to obtain a straight-line plane drawing. The aim is to move as few vertices as possible. We present an algorithm that untangles the cycle graph C n while keeping Ω(n 2/3) vertices fixed.

For any connected graph G, we also present an upper bound on the number of fixed vertices in the worst case. The bound is a function of the number of vertices, maximum degree, and diameter of G. One consequence is that every 3-connected planar graph has a drawing δ such that at most O((nlog n)2/3) vertices are fixed in every untangling of δ.

Supported by project MSM0021620838 of the Czech Ministry of Education.