tarjan求LCA模板

Posted 2020-10-24 mybing

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<ctime>
#include<algorithm>
#include<string>
#include<queue>
using namespace std;
int n,m;
int f[400001],lin1[400001],lin2[400001],len1=0,len2=0;
bool vis[400001];
struct one
{
    int y,next,zhi;
};
one e1[400001];
one e2[400001];
void insert1(int aa,int bb)
{
    e1[++len1].next=lin1[aa];
    lin1[aa]=len1;
    e1[len1].y=bb;
}
void insert2(int aa,int bb)
{
    e2[++len2].next=lin2[aa];
    lin2[aa]=len2;
    e2[len2].y=bb;
}
int findit(int p)
{
    while(p!=f[p])
    {
        p=f[p];
    }
    return p;
}
void Tarjan(int p)
{
    vis[p]=true;
    for(int i=lin1[p];i;i=e1[i].next)
    {
        if(vis[e1[i].y])continue;
        Tarjan(e1[i].y);
        f[e1[i].y]=p;
    }
    for(int i=lin2[p];i;i=e2[i].next)
    {
        if(vis[e2[i].y])
        e2[i].zhi=findit(e2[i].y);
    }
}
int main()
{
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m*2;i++)e2[i].zhi=0;
    for(int i=1;i<=n;i++)
    {
        f[i]=i;
        vis[i]=false;
    }
    for(int i=1;i<=n-1;i++)
    {int aa,bb;
    scanf("%d%d",&aa,&bb);
    insert1(aa,bb);
    insert1(bb,aa);
    }
    for(int i=1;i<=m;i++)
    {
        int aa,bb;
        scanf("%d%d",&aa,&bb);
        insert2(aa,bb);
        insert2(bb,aa);
    }
    vis[1]=true;
    Tarjan(1);
    for(int i=1;i<=m*2;i+=2)
    {
        cout<<max(e2[i].zhi,e2[i+1].zhi)<<endl;
    }
    return 0;
}