贪心+并查集
fighting~~~~~！！
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 }