hdu 1598 find the most comfortable road

 1 #include<iostream>
 2 #include<algorithm>
 3 #include<cmath>
 4 #include<cstdio>
 5 using namespace std;
 6 #define maxn 300
 7 #define INF 0x3fffffff
 8 int par[maxn];
 9 int n,m;
10 
11 struct node
12 {
13     int x;
14     int y;
15     int w;
16 };
17 node e[maxn * maxn / 2];
18 int cmp(const node& a,const node &b)
19 {
20     return a.w < b.w;
21 }
22 void init()
23 {
24     for(int i = 1; i <= n; i++)
25         par[i] = i;
26 }
27 int Find(int x)
28 {
29     int t,r,k;
30     k = x;
31     while(x != par[x])
32         x = par[x];
33     while(k != x)//tanta
34     {
35         t = par[k];
36         par[k] = x;
37         k = t;
38     }
39     return x;
40 }
41 void Merge(int x,int y)
42 {
43     int a = Find(x);
44     int b = Find(y);
45     if(a != b)
46     {
47         par[a] = b;
48     }
49 }
50 void kruskal()
51 {
52     int q,st,en,mindis,i,j;
53     while(cin>>n>>m)
54     {
55         for(int i = 0; i < m; i++)
56             cin>>e[i].x>>e[i].y>>e[i].w;
57         sort(e,e+m,cmp);
58         cin>>q;
59         while(q--)
60         {
61             cin>>st>>en;
62             mindis = INF;
63             for(i = 0; i < m ; i++)//meijuzuixiao
64             {
65                 init();
66                 for(j = i; j < m; j++)//zhaozuidabian
67                 {
68                     Merge(e[j].x,e[j].y);
69                     if(Find(st) == Find(en))//起点终点相连
70                     {
71                         mindis = min(mindis,e[j].w - e[i].w);
72                         break;
73                     }
74                 }
75                 if(j == m) break; //j == m 继续枚举也不可能找到
76             }
77             if(mindis != INF) cout<<mindis<<endl;
78             else cout<<"-1"<<endl;
79         }
80     }
81 }
82 int main()
83 {
84     freopen("input.txt","r",stdin);
85     kruskal();
86     return 0;
87 }