We study the problem of decomposing the vertex set
V of a graph into two nonempty parts
V1,V2 which induce subgraphs where each vertex
140d13418e9771" title="Click to view the MathML source">vV1 has degree at least
3440036270" title="Click to view the MathML source">a(v) inside
V1 and each
vV2 has degree at least
b(v) inside
V2. We give a polynomial-time algorithm for graphs with bounded treewidth which decides if a graph admits a decomposition, and gives such a decomposition if it exists. This result and its variants are then applied to designing polynomial-time approximation schemes for planar graphs where a decomposition does not necessarily exist but the local degree conditions should be met for as many vertices as possible.