uva 11354 bond 最小生成树

#include <cstdio>
#include <cstring>
#include <vector>
#include <algorithm>
using namespace std;
#define maxn  100000 + 10
struct Edge
{
    int u,v,w;
}e[100100];
int cmp(Edge a,Edge b)
{
    return a.w<b.w;
}
int n,m;
vector <int> G[maxn],C[maxn];
int pa[maxn],fa[maxn],cost[maxn],L[maxn];
int anc[maxn][20],maxcost[maxn][20];
int find(int x)
{
    if(pa[x]==x) return x;
    else return pa[x]=find(pa[x]);
}
void dfs(int u,int father,int level)
{
    int i;
    L[u]=level;
    for(i=0;i<G[u].size();i++)
    {
        int v=G[u][i];
        if(v!=father)
        {
            fa[v]=u;
            cost[v]=C[u][i];
            dfs(v,u,level+1);
        }
    }
}
void pre()
{
    int i,j;
    for(i=0;i<n;i++)
    {
        anc[i][0]=fa[i];maxcost[i][0]=cost[i];
        for(j=1;(1<<j)<n;j++) anc[i][j]=-1;
    }
    for(j=1;(1<<j)<n;j++)
        for(i=0;i<n;i++)
        {
            if(anc[i][j-1]!=-1)
            {
                int a=anc[i][j-1];
                anc[i][j]=anc[a][j-1];
                maxcost[i][j]=max(maxcost[i][j-1],maxcost[a][j-1]);
            }
        }
}
int query(int p,int q)
{
    int tmp,log,i;
    if(L[p]<L[q]) swap(p, q);
    for(log=1;(1<<log)<=L[p];log++);log--;
    int ans=-1000000000;
    for(i=log;i>=0;i--)
        if(L[p]-(1<<i)>=L[q])
        {
            ans=max(ans,maxcost[p][i]);
            p=anc[p][i];
        }
    if(p==q) return ans;
    for(i=log;i>=0;i--)
    {
        if(anc[p][i]!=-1&&anc[p][i]!=anc[q][i])
        {
            ans=max(ans,maxcost[p][i]);p=anc[p][i];
            ans=max(ans,maxcost[q][i]);q=anc[q][i];
        }
    }
    ans=max(ans,cost[p]);
    ans=max(ans,cost[q]);
    return ans;
}
int main()
{
    int kcas=0;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        int i,j;
        int x,y,d;
        for(i=0;i<m;i++)
        {
            scanf("%d%d%d",&x,&y,&d);
            e[i].u=x-1;
            e[i].v=y-1;
            e[i].w=d;
        }
        sort(e,e+m,cmp);
        for(i=0;i<n;i++) {pa[i]=i;G[i].clear();C[i].clear();}
        for(i=0;i<m;i++)
        {
            x=e[i].u;
            y=e[i].v;
            d=e[i].w;
            int fx=find(x);
            int fy=find(y);
            if(fx!=fy)
            {
                pa[fx]=fy;
                G[x].push_back(y);C[x].push_back(d);
                G[y].push_back(x);C[y].push_back(d);
            }
        }
        dfs(0,-1,0);
        pre();
        int que;
        if(++kcas!=1) printf("\n");
        scanf("%d",&que);
        while(que--)
        {
            scanf("%d%d",&x,&y);
            printf("%d\n",query(x-1,y-1));
        }
    }
    return 0;
}