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;
	}
}