P1967 货车运输 未完成

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 #include<cmath>
 #include<algorithm>
 using namespace std;
 const int MAXN=;
 int n,m;
 int x,y,z;
 struct node
 {
     int u,v,w,next;
 }edge[MAXN],a[MAXN];
 int num=;
 int head[MAXN];
 int f[MAXN];
 int anum=;
 int ahead[MAXN];
 int deep[MAXN];
 int s[MAXN][];
 int take[MAXN][];
 void edge_add(int x,int y,int z)
 {
     edge[num].u=x;
     edge[num].v=y;
     edge[num].w=z;
     edge[num].next=head[x];
     head[x]=num++;
 }
 void a_add(int i)
 {
     a[anum].u=edge[i].u;
     a[anum].v=edge[i].v;
     a[anum].w=edge[i].w;
     a[anum].next=ahead[a[anum].u];
     ahead[a[anum].u]=anum++;
 }
 int comp(const node & a ,const node & b)
 {return a.w>b.w;}

 int find(int x)
 {
     if(f[x]!=x)
     f[x]=find(f[x]);
     return f[x];
 }
 void unionn(int x,int y)
 {
     int fx=find(x);
     int fy=find(y);
     f[fx]=fy;
 }
 void Biggest_Kruskal()
 {
     sort(edge+,edge+num,comp);
     int k=;
     for(int i=;i<num;i++)
     {
         int uu=edge[i].u;
         int vv=edge[i].v;
         if(find(uu)!=find(vv))
         {
             unionn(uu,vv);
             a_add(i);
             k++;
         }
         if(k==n-)break;
     }
     for(int i=;i<=anum;i++)
         cout<<a[i].u<<" "<<a[i].v<<" "<<a[i].w<<" "<<a[i].next<<endl;
 }
 void Build_Tree(int p)
 {
     for(int i=ahead[p];i!=-;i=a[i].next)
     {
         int will=a[i].v;
         if(deep[will]==)
         {
             deep[will]=deep[p]+;
             s[will][]=p;
             take[will][]=a[i].w;
             Build_Tree(will);
         }
     }
 }
 void Initialize_Step()
 {
     for(int i=;i<=;i++)
     {
         for(int j=;j<=n;j++)
         {
             s[j][i]=s[s[j][i-]][i-];
             take[j][i]=min(take[j][i-],take[s[j][i-]][i-]);
         }
     }
 }
 int LCA(int x,int y)
 {
     int ans=0x7ff;
     if(deep[x]<deep[y])
     swap(x,y);
     for(int i=;i>=;i--)
     {
         if(deep[s[x][i]]>=deep[y])
         x=s[x][i];
     }
     if(x==y)
     return x;
     for(int i=;i>=;i--)
     {
         if(s[x][i]!=s[y][i])
         {
             x=s[x][i];
             y=s[y][i];
             ans=min(ans,take[x][i]);
             ans=min(ans,take[y][i]);
         }
     }
     ans=min(ans,take[x][]);
     ans=min(ans,take[y][]);
     return ans;
 }
 int main()
 {
     scanf("%d%d",&n,&m);

     for(int i=;i<=n;i++)
     {head[i]=-;f[i]=i;ahead[i]=-;}

     for(int i=;i<=m;i++)
     {
         scanf("%d%d%d",&x,&y,&z);
         edge_add(x,y,z);
         //edge_add(y,x,z);
     }
     Biggest_Kruskal();
     deep[]=;
     for(int i=;i<=n;i++)
     Build_Tree(i);
     Initialize_Step();
     int q;
     scanf("%d",&q);
     for(int i=;i<=q;i++)
     {
         int x,y;
         scanf("%d%d",&x,&y);
         if(find(x)!=find(y))
         {
             printf("-1\n");
             continue;
         }
         printf("%d\n",LCA(x,y));
     }
     return ;
 }