2017-12-10 targan求LCA

#include<iostream>

#include<cstdio>
#include<cstring>
#include<cctype>
using namespace std;
const int M=1000000+10;
struct edge
{
int next,to;
}tree[M];
struct node 
{
int next,to,index;
}que[M];
bool vis[M];
int n,m,s,a,b,ans[M],father[M];
int cnt_tree,head_tree[M],cnt_que,head_que[M];
void add_tree(int u,int v)
{
tree[++cnt_tree].next=head_tree[u];
tree[cnt_tree].to=v;
head_tree[u]=cnt_tree;
}
void add_que(int u,int v,int base)
{
que[++cnt_que].next=head_que[u];
que[cnt_que].to=v;
que[cnt_que].index=base;
head_que[u]=cnt_que;
}
int find(int x)
{
if(father[x]!=x)return father[x]=find(father[x]);
return x;
}
void targan(int x)
{
vis[x]=1;
for(int i=head_tree[x];i;i=tree[i].next)
{
int y=tree[i].to;
if(!vis[y])
{
targan(y);
father[y]=x;
}
}
for(int i=head_que[x];i;i=que[i].next)
{
int y=que[i].to;
if(vis[y]);
ans[que[i].index]=find(y);
}
}
void read(int &a)
{
char c=getchar();
while(!isdigit(c)) c=getchar();
while(isdigit(c))a=a*10+c-48,c=getchar();
}
int main()
{
//freopen("LCA.in","r",stdin);
//freopen("LCA.out","w",stdout);
read(n),read(m),read(s);
for(int i=1;i<=n-1;++i)
{
read(a=0),read(b=0);
add_tree(a,b);
add_tree(b,a);
}
for(int i=1;i<=m;++i)
{
read(a=0),read(b=0);
add_que(b,a,i);
add_que(a,b,i);
}
for(int i=1;i<=n;++i)
father[i]=i;
targan(s);
for(int i=1;i<=m;++i)
printf("%d\n",ans[i]);
// fclose(stdin);
// fclose(stdout);
return 0;
}