设G=(V,E)是一个图,对G的每一点v给一颜色集L(v).G称为L列表可染的,如果存在G的点染色f满足:f(u)≠f(v),任意(u,v)∈E(G),且f(u)∈L(u),任意u∈V(G).G称为k可选择的,对于任何列表L(v)(这里每一个L(v)恰有k个元素)G都是L列表可染的.本文研究了没有某些圈的平面图的可选择性,证明了没有4,5,7,10圈的平面图是3可选择的.
For a graph G= (V,E) ,every vertex v of G is assigned a color set L(v). G is called L-list colorable if there is a coloring f of vertices of G with f(u) ≠6 f(v), arbitary ( u, v) ∈ E(G) and f(u) ∈ L( u), arbitary u ∈ V(G). G is called k-choosahle if G is L-list-colorahle for any assignment of lists L(v) where each L(v) has exactly k elements. In this paper, we prove that every planar graph without i-cycles for each i∈{4,5,7,10 } is 3-choosahle.