题目连接： http://acm.hdu.edu.cn/showproblem.php?pid=1598

find the most comfortable road

4 4
1 2 2
2 3 4
1 4 1
3 4 2
2
1 3
1 2

1
0

import java.io.*;
import java.util.*;
public class Main {
	int MIN=Integer.MAX_VALUE;
	int M=205,n,m;
	int patten[]=new int[M];
	Node node[];
	public static void main(String[] args) {
		new Main().work();
	}
	void work(){
		Scanner sc=new Scanner(new BufferedInputStream(System.in));
		while(sc.hasNext()){
			n=sc.nextInt();
			m=sc.nextInt();
			init();
			node=new Node[m];
			for(int i=0;i<m;i++){
				int a=sc.nextInt();
				int b=sc.nextInt();
				int c=sc.nextInt();
				node[i]=new Node(a,b,c);
				union(a,b);
			}
			Arrays.sort(node);//按权值排序
			int q=sc.nextInt();
			for(int i=0;i<q;i++){
				int a=sc.nextInt();
				int b=sc.nextInt();
				getDistance(a,b);
			}
		}
	}
	//获取最短距离
	void getDistance(int a,int b){
		int min=MIN;
		for(int i=0;i<m;i++){
			init();
			for(int j=i;j<m;j++){ 
				union(node[j].a,node[j].b);
				if(find(a)==find(b))
					min=Math.min(min,node[j].c-node[i].c);
			}
		}
		if(min!=MIN)
			System.out.println(min);
		else
			System.out.println(-1);
	}
	// 合并
	void union(int a,int b){
		int pa=find(a);
		int pb=find(b);
		if(pa==pb)
			return;
		patten[pa]=pb;
	}
	//查找
	int find(int x){
		if(patten[x]==x)
			return x;
		patten[x]=find(patten[x]);
		return patten[x];
	}
	//初始化
	void init(){
		for(int i=0;i<=n;i++){
			patten[i]=i;
		}
	}
	class Node implements Comparable<Node>{
		int a;
		int b;
		int c;
		Node(int a,int b,int c){
			this.a=a;
			this.b=b;
			this.c=c;
		}
		public int compareTo(Node o) {
			return this.c>o.c?1:-1;
		}
	}
}