最小生成树 Kruskal算法 java代码实现

/*
*日期:2010-04-18 20:02
*开发者:heroyan
*联系方式:zndxysf@126.com
*功能:无向图最小生成树Kruskal算法实现案例
*/
import java.util.Scanner;
import java.util.Arrays;
import java.util.ArrayList;
public class 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 Kruskal(){}

public static void main(String args[]){
Kruskal sp = new 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("spanning tree begin!Input the node number:");
n = scan.nextInt();
System.out.println("Input the graph(-1,-1,-1 to exit)");

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);
m