Welch_Powell图的顶点着色算法，O(n3)

import java.util.Arrays;

class Vertex implements Comparable {
    int color;
    int degree;

    @Override
    public int compareTo(Vertex o) {
        return o.degree-this.degree;
    }
}


public class Welch_Powell_Color {

    final static int MAX=100;

    int c[][];
    int n;



    // 排序前的副本
    Vertex copys[];


    // 按顶点度数从大到小排序
    boolean cmp(Vertex a, Vertex b)
    {
        return a.degree > b.degree;
    }
    private void sortByDegree(Vertex[] vertex) {
        Arrays.sort(vertex);
    }


    public void welsh_powell(Vertex[] vertex, int[][] edges) {
        //按度数降序排列
        sortByDegree(vertex);
        int colored_cnt=0;
        int ncolor=0;
        while (colored_cnt < n) {
            ncolor++;
            for (int i = 1; i <= n; i++) {
                // 如果没有着色
                if (vertex[i].color == 0) {
                    boolean ok = true;
                    for (int j = 1; j <= n; j++) {
                        // 如果相邻顶点有相同颜色
                        if (edges[i][j]==1&&vertex[j].color==ncolor) {
                            ok = false;
                            break;
                        }
                    }
                    // 相邻顶点有相同颜色，直接跳过
                    if (!ok)
                        continue;
                    // 相邻顶点没有相同颜色，则对当前节点着色
                    vertex[i].color = ncolor;
                    colored_cnt++;
                }
            }
        }
    }



}