题意:
裸LCA
题解:
tarjan离线解LCA模板...
Program:
#include<iostream>
#include<stdio.h>
#include<math.h>
#include<string.h>
#include<string>
#include<queue>
#include<map>
#include<algorithm>
#define MAXN 100005
#define ll long long
#define oo 1e+10
#define eps 1e-10
using namespace std;
struct node
{
int u,v,id,next;
}edge[MAXN],Qedge[MAXN<<1];
map<string,int> H;
int En,Vn,_next[MAXN],D[MAXN],father[MAXN];
int Qen,Qnext[MAXN],ans[MAXN];
bool visited[MAXN];
char st[MAXN];
string s,name[MAXN];
int getdata()
{
scanf("%s",st),s=st;
if (H.find(s)==H.end()) H[s]=++Vn,name[Vn]=s;
return H[s];
}
void addedgeE(int u,int v)
{
edge[++En].next=_next[u],_next[u]=En;
edge[En].v=v;
}
void addedgeQ(int u,int v,int id)
{
Qedge[++Qen].next=Qnext[u],Qnext[u]=Qen;
Qedge[Qen].v=v,Qedge[Qen].id=id;
}
int getfather(int u)
{
if (father[u]==u) return u;
return father[u]=getfather(father[u]);
}
void tarjan(int u)
{
int k,v,id;
father[u]=u;
visited[u]=true;
for (k=Qnext[u];k;k=Qedge[k].next)
{
v=Qedge[k].v,id=Qedge[k].id;
if (!visited[v]) continue;
ans[id]=getfather(v);
}
for (k=_next[u];k;k=edge[k].next)
{
v=edge[k].v;
tarjan(v);
father[v]=u;
}
}
int main()
{
int n,Q,i,u,v;
string s;
scanf("%d",&n),Vn=0,H.clear();
memset(_next,0,sizeof(_next)),En=0;
memset(D,0,sizeof(D));
while (n--)
{
u=getdata(),v=getdata();
D[v]++;
addedgeE(u,v);
}
scanf("%d",&Q);
memset(Qnext,0,sizeof(Qnext)),Qen=0;
for (i=1;i<=Q;i++)
{
u=getdata(),v=getdata();
addedgeQ(u,v,i),addedgeQ(v,u,i);
}
memset(visited,0,sizeof(visited));
tarjan(1);
for (i=1;i<=Q;i++) puts(name[ans[i]].c_str());
return 0;
}
