hdu1233还是畅通工程

首先按每两个村庄的距离从小到大排序，因为最小距离的那条道路是必建造的；每输入两个数，看他俩的老大是否一样，如果一样的话，说明这两已经连通了，不需要建造了，反之则建造。

import java.util.Arrays;
import java.util.Scanner;
 
public class hdu1233 {
 
    public static void main(String[] args) {
        // TODO 自动生成的方法存根
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()) {
            int n = sc.nextInt();
            if (n==0) {
                break;
            }
             
            int[] lda = new int[n+1];
            for (int i = 0; i < lda.length; i++) {
                lda[i] = i;
                 
            }
            n = n*(n-1)/2;
            Node4[] aa = new Node4[n];
            for (int i = 0; i < n; i++) {
                int a = sc.nextInt();
                int b = sc.nextInt();
                int c = sc.nextInt();               
                aa[i] = new Node4(a, b, c);         
            }
            Arrays.sort(aa,0,n);
 
            int res = 0;
            for (int i = 0; i < n; i++) {
                int x = find(aa[i].x, lda);
                int y = find(aa[i].y, lda);
                if (x != y) {
                    lda[x] = y;
                    res += aa[i].z;
                }               
            }
            System.out.println(res);
        }
        sc.close();
    }
     
    //找老大
    public static int find(int x,int[] lda) {
        int index = x;
        while (lda[index]!=index) {
            index = lda[index];         
        }
        return index;
    }
}
class Node4 implements Comparable<Node4>{
    public int x;
    public int y;
    public int z;
    Node4(int x,int y,int z) {
        this.x = x;
        this.y = y;
        this.z = z;
    }
    @Override
    public int compareTo(Node4 o) {
        // TODO 自动生成的方法存根
        //按照z从小到大排列
        return this.z - o.z;
    }
}