模板_LCA(最近公共祖先)

#include<cstdio>
#include<vector>
#include<algorithm>
#include<iostream>
using namespace std;
#define N 100005
#define M 21
struct LCA{
vector<int> g
;
int root,ans,n,m;
int d
,f
[M];

void dfs(int x,int dp){
d[x]=dp;
for(int i=0;i<g[x].size();i++){
if(!d[g[x][i]]){
dfs(g[x][i],dp+1);
f[g[x][i]][0]=x;
}
}
}

void work(){
for(int i=1;i<=20;i++)
for(int j=1;j<=n;j++)
f[j][i]=f[f[j][i-1]][i-1];
}

int lca(int u,int v){
if(d[u]<d[v])   swap(u,v);
int l=d[u]-d[v];
if(l)
for(int i=0;i<=20;i++)
if(l&(1<<i))    u=f[u][i];
if(u==v) return u;
for(int i=20;i>=0;i--){
if(f[u][i]!=f[v][i])
u=f[u][i],v=f[v][i];
}
return f[u][0];
}

void init(){
scanf("%d",&n);int x,y;
for(int i=1;i<=n;i++){
scanf("%d",&x);
if(x) g[x].push_back(i);
else root=i;
}
dfs(root,0);work();ans=0;
scanf("%d",&m);
while(m--){
scanf("%d%d",&x,&y);
ans=lca(x^ans,y^ans);
printf("%d\n",ans);
}
}
}s;
int main(){
s.init();
return 0;
}

#include<cstdio>
#include<cstring>
#include<queue>
#include<vector>
#include<iostream>
using namespace std;
#define N 40005
struct Tarjan{
struct qEdge{int fr,to,lca;};
struct Edge{int fr,to,dis;};
vector<Edge> edge;vector<qEdge> qedge;
vector<int> qs
;vector<int> g
;
int p
;long long d
,ans
;bool b
;int n,m;

void Add_qEdge(int fr,int to){
qedge.push_back((qEdge){fr,to,0});
int ll=qedge.size();
qs[fr].push_back(ll-1);
qs[to].push_back(ll-1);
}

void Add_Edge(int fr,int to,int d){
edge.push_back((Edge){fr,to,d});edge.push_back((Edge){to,fr,d});
m=edge.size();
g[fr].push_back(m-2);g[to].push_back(m-1);
}

long long abs(long long x){return x>=0?x:-x;}

void dfs(int u,int f,long long w){
d[u]=w;
for(int i=0;i<g[u].size();i++){
Edge &e=edge[g[u][i]];
if(e.to==f) continue;
dfs(e.to,u,w+e.dis);
}
}

int Find(int x){return p[x]==x?x:p[x]=Find(p[x]);}

void Tarjan_Lca(int u){
p[u]=u;b[u]=true;
for(int i=0;i<g[u].size();i++){
Edge &e=edge[g[u][i]];
if(!b[e.to]){
Tarjan_Lca(e.to);
p[e.to]=u;
}
}
for(int i=0;i<qs[u].size();i++){
qEdge &e=qedge[qs[u][i]];
if(u==e.fr&&b[e.to]){
e.lca=Find(e.to);
ans[qs[u][i]]=abs(d[u]+d[e.to]-2*d[e.lca]);
}
if(u==e.to&&b[e.fr]){
e.lca=Find(e.fr);
ans[qs[u][i]]=abs(d[u]+d[e.fr]-2*d[e.lca]);
}
}
}

void init(){
edge.clear();qedge.clear();
for(int i=0;i<=n;i++) g[i].clear(),qs[i].clear();
memset(d,0,sizeof(d));memset(ans,0,sizeof(ans));
};

void Solve(int n,int m){
this->n=n;this->m=m;int x,y,z;
for(int i=0;i<=n;i++) p[i]=i;
for(int i=1;i<n;i++){
scanf("%d%d%d",&x,&y,&z);
Add_Edge(x,y,z);
}
for(int i=0;i<m;i++){
scanf("%d%d",&x,&y);
Add_qEdge(x,y);
}
dfs(1,0,0);Tarjan_Lca(1);
for(int i=0;i<m;i++) printf("%lld\n",ans[i]);
init();
}

}s;
int main(){
int t,n,m;scanf("%d",&t);
while(t--){
scanf("%d%d",&n,&m);
s.Solve(n,m);
}
return 0;
}