Kruskal算法求最小生成树(java)

Kruskal算法求最小生成树（JA V A）
代码：
package homework;
import java.util.Scanner;
import java.util.Arrays;
import java.util.ArrayList;
class Edge {
public int start;//始边
public int end;//终边
public double cost;//权重
}
public class MinSpanningTree_Kruskal{
private static int MAX = 100;
private ArrayList<Edge> edge = new ArrayList<Edge>();//整个图的边
private ArrayList<Edge> target = new ArrayList<Edge>();//目标边，最小生成树private int[] parent = new int[MAX];//标志所在的集合
private static double INFINITY = 99999999.99;//定义无穷大
private double mincost = 0.0;//最小成本
private int n;//结点个数
public MinSpanningTree_Kruskal(){}
public static void main(String args[]){
MinSpanningTree_Kruskal sp = new MinSpanningTree_Kruskal();
sp.init();
sp.kruskal();
sp.print();
}//初始化
public void init(){
Scanner scan = new Scanner(System.in);
int p,q;
double w;
System.out.println("请输入结点个数：");
n = scan.nextInt();
System.out.println("请输入各条边及权值（每次输入一组数据按回车确认，" +
"最后输入-1 -1 -1 结束输入过程）");
while(true){
p = scan.nextInt();
q = scan.nextInt();
w = scan.nextDouble();
if(p < 0 || q < 0 || w < 0){
break;
}
Edge e = new Edge();
e.start = p; e.end = q; e.cost = w;
edge.add(e);
}
mincost = 0.0;
for(int i = 1; i <= n; ++i){
parent[i] = i;
}
}//集合合并
public void union(int j, int k){
for(int i = 1; i <= n; ++i){
if(parent[i] == j){
parent[i] = k;
}
}
}//prim算法主体
public void kruskal(){
//找剩下的n-2条边
int i = 0;
while(i < n-1 && edge.size() > 0){
//每次取一最小边，并删除
double min = INFINITY;
int tag = 0;
Edge tmp = null;
for(int j = 0; j < edge.size(); ++j){
Edge tt = edge.get(j);
if(tt.cost < min){
min = tt.cost;
tmp = tt;
}
}
int jj = parent[tmp.start];
int kk = parent[tmp.end];
//去掉环
if(jj != kk){
++i;
target.add(tmp);
mincost += tmp.cost;
union(jj,kk);
}
edge.remove(tmp);
}
if(i != n-1){
System.out.println("没有最小生成树");
System.exit(0);
}
}//打印结果
public void print(){
double sum=0;
System.out.println("最小生成树：");
for(int i = 0; i < target.size(); ++i){
Edge e = target.get(i);
System.out.println("第" + (i+1) + "条边: " + e.start + "---" + e.end
+ " 权值：" + e.cost);
sum=sum+e.cost;
}
System.out.println("最小生成树的权值：" + sum);
}
}
调试结果：。