BZOJ 1787: [Ahoi2008]Meet 紧急集合 LCA

1787: [Ahoi2008]Meet 紧急集合

Description

///1085422276

#include<bits/stdc++.h>
using namespace std;
//#pragma comment(linker, "/STACK:102400000,102400000")
using namespace std ;
typedef long long ll;
#define mem(a) memset(a,0,sizeof(a))
#define pb push_back
inline ll read()
{
ll x=0,f=1;char ch=getchar();
while(ch<'0'||ch>'9'){
if(ch=='-')f=-1;ch=getchar();
}
while(ch>='0'&&ch<='9'){
x=x*10+ch-'0';ch=getchar();
}return x*f;
}
//****************************************
const int  N=500500;
#define mod 1000000007
#define inf 1000000007
int n,m,head
,t,vis
,deep
,fa
[20];
struct ss {
int to,next;
}e[N*2];
void add(int u,int v) {
e[t].next=head[u];e[t].to=v;head[u]=t++;
}
void init() {
t=1;mem(head);mem(vis);mem(fa);mem(deep);
}
void dfs(int x) {
vis[x]=1;
for (int i=1; i<=18 ;i++) {
if(deep[x]<(1<<i)) break;
fa[x][i] = fa[fa[x][i-1]][i-1];
}
for (int i=head[x];i;i=e[i].next) {
if(vis[e[i].to]) continue;
deep[e[i].to]=deep[x]+1;
fa[e[i].to][0]=x;
dfs(e[i].to);
}
}
int RMQ_LCA(int x,int y) {
if(deep[x]<deep[y]) swap(x,y);
int d=deep[x]-deep[y];
for (int i=0; i<=18 ;i++)
if((1<<i)&d) x=fa[x][i];
for (int i=18; i>=0 ;i--) {
if(fa[x][i]!=fa[y][i]) {
x=fa[x][i];y=fa[y][i];
}
}
if(x==y) return x;
else return fa[x][0];
}
int Dis_LCA(int x,int y) {
int LCA= RMQ_LCA(x,y);
return (deep[x]+deep[y]-2*deep[LCA]);
}
int cal(int x,int y,int z)  {
int A;
int L1=RMQ_LCA(x,y);
int L2=RMQ_LCA(y,z);
int L3=RMQ_LCA(x,z);
if(L1==L2) {
A=L3;
}
else if(L2==L3) {
A=L1;
}
else A=L2;
int anss=Dis_LCA(x,A)+Dis_LCA(y,A)+Dis_LCA(z,A);
printf("%d %d\n",A,anss);
//cout<<A<<" "<<anss<<endl;
}
int main() {
scanf("%d%d",&n,&m);
init();
for(int i=1;i<n;i++) {
int u,v;
scanf("%d%d",&u,&v);
add(u,v);add(v,u);
}
dfs(1);
for(int i=1;i<=m;i++) {
int a,b,c;
scanf("%d%d%d",&a,&b,&c);
cal(a,b,c);
}

return 0;
}