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 111111 #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 }