hdu 1598 find the most comfortable road

 1 #include "iostream"
 2 #include "algorithm"
 3 #include "memory.h"
 4 #include "cmath"
 5 #include "string"
 6 #include "vector"
 7 #include "algorithm"
 8 #include "climits"
 9 using namespace std;
10 #define MAXN 1111
11 #define _min(a,b) (((a)<(b))?(a):(b))
12 struct node {
13     int x, y,speed;
14     bool operator < (node a) const{
15         return speed < a.speed;
16     }
17 }p[MAXN];
18 int fa[MAXN];
19 int n, m, q, t;
20 int re, num, ans;
21 
22 int find(int x)
23 {
24     if (fa[x] < 0) return x;
25     return fa[x] = find(fa[x]);
26 }
27 
28 void merge(int a, int b)
29 {
30     int x = find(a);
31     int y = find(b);
32     if (x < y) {
33         fa[x] += fa[y];
34         fa[y] = x;
35     }
36     if (x > y) {
37         fa[y] += fa[x];
38         fa[x] = y;
39     }
40 }
41 
42 
43 int main()
44 {
45     ios::sync_with_stdio(false);
46     while (cin >> n >> m) {
47         for (int i = 0; i < m; ++ i) {
48             cin >> p[i].x >> p[i].y >> p[i].speed;
49         }
50         sort(p,p+m);
51         cin >> q;
52         for (int i = 0; i < q; ++i) {
53             int u, v;
54             cin >> u >> v;
55             ans = INT_MAX;
56             for (int j = 0; j < m; ++j) {
57                 memset(fa,-1,sizeof(fa));
58                 for (int k = j; k < m; ++k) {
59                     merge(p[k].x,p[k].y);
60                     if (find(u) == find(v)) {
61                         ans = _min(ans, p[k].speed - p[j].speed);
62                         break;
63                     }
64                 }
65             }
66             if (ans == INT_MAX) cout << "-1" << endl;
67             else cout << ans << endl;
68         }
69     }
70     return 0;
71 }