AC日记——货车运输 codevs

#include<cstdio>
#include<algorithm>

using namespace std;

struct node {
    int from,to,dis,next;
};
struct node usee[60001];
struct node edge[20001];
int n,m,head[10001],num=0;
int f[10001],bnum=0,tail=0;
int cur=0,dfn[10001],tarjan_dfn=0;

int max(int a,int b){return a>b?a:b;}

int min(int a,int b){return a<b?a:b;}

void tarjan(int scre,int before)
{
    tarjan_dfn++;
    dfn[scre]=tarjan_dfn;
    for(int i=head[scre];i!=0;i=edge[i].next)
    {
        if(edge[i].to!=before)
        {
            tarjan(edge[i].to,scre);
        }
    }
}

int tarjan_lca(int minn,int maxn)
{
    int kop=minn,kol=maxn,kcc=1e18;
    while(dfn[kol]>dfn[minn])
    {
        for(int i=head[kol];i!=0;i=edge[i].next)
        {
            if(dfn[edge[i].to]<dfn[kol])
            {
                kol=edge[i].to;
                kcc=min(kcc,edge[i].dis);
                break;
            }
        }
    }
    while(dfn[kop]>dfn[kol])
    {
        for(int i=head[kop];i!=0;i=edge[i].next)
        {
            if(dfn[edge[i].to]<dfn[kop])
            {
                kop=edge[i].to;
                kcc=min(kcc,edge[i].dis);
                break;
            }
        }
    }
    return kcc;
}

int cmp(struct node a,struct node b){return a.dis>b.dis;}

void edge_add(int from,int to,int dis)
{
    num++;
    edge[num].to=to;
    edge[num].dis=dis;
    edge[num].from=from;
    edge[num].next=head[from];
    head[from]=num;
}

int find(int x)
{
    if(x==f[x]) return f[x];
    else return f[x]=find(f[x]);
}

int qread()
{
    int x=0;char ch=getchar();
    while(ch>‘9‘||ch<‘0‘) ch=getchar();
    while(ch<=‘9‘&&ch>=‘0‘){x=x*10+(int)(ch-‘0‘);ch=getchar();}
    return x;
}

int main()
{
    n=qread(),m=qread();
    for(int i=1;i<n;i++)
    {
        f[i]=i;
        bnum++;
        usee[bnum].from=i;
        usee[bnum].to=i+1;
        usee[bnum].dis=-1;
    }
    f[n]=n;
    int from,to,dis;
    for(int i=1;i<=m;i++)
    {
        from=qread(),to=qread(),dis=qread();
        bnum++;
        usee[bnum].to=to;
        usee[bnum].dis=dis;
        usee[bnum].from=from;
    }
    sort(usee+1,usee+bnum+1,cmp);
    int x,y;
    while(tail<n-1)
    {
        cur++;
        x=find(usee[cur].from),y=find(usee[cur].to);
        if(x!=y)
        {
            tail++;
            edge_add(usee[cur].from,usee[cur].to,usee[cur].dis);
            edge_add(usee[cur].to,usee[cur].from,usee[cur].dis);
            f[x]=y;
        }
    }
    tarjan(1,0);
    int q=qread();
    while(q--)
    {
        from=qread(),to=qread();
        dfn[from]<dfn[to]?printf("%d\n",tarjan_lca(from,to)):printf("%d\n",tarjan_lca(to,from));
    }
    return 0;
}