树链剖分
强烈安利一个树链剖分入门讲解代码
（手动感谢这位神仙QWQ，窝才刚入门啊QAQ）
（最水的一篇博客，不接受反驳）
P3384 【模板】树链剖分
代码
#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<string>
#include<cstring>
#include<cstdlib>
#include<queue>
using namespace std;
inline int read()
{
int ans=0;
char last=' ',ch=getchar();
while(ch<'0'||ch>'9') last=ch,ch=getchar();
while(ch>='0'&&ch<='9') ans=ans*10+ch-'0',ch=getchar();
if(last=='-') ans=-ans;
return ans;
}
const int maxn=1e5+10;
int n,m,r,mod;
int w[maxn],wt[maxn];
int fa[maxn],son[maxn],size[maxn],dfn[maxn],dep[maxn],top[maxn],tim=0;
int sum[maxn<<2],laz[maxn<<2];
int head[maxn],cnt=0;
struct node{
int nxt,to;
}edge[maxn<<2];
inline void addedge(int a,int b)
{
edge[++cnt].to =b;edge[cnt].nxt =head[a];head[a]=cnt;
edge[++cnt].to =a;edge[cnt].nxt =head[b];head[b]=cnt;
}
inline void dfs1(int u,int f)
{
fa[u]=f;
son[u]=0;
size[u]=1;
for(int i=head[u];i;i=edge[i].nxt )
{
int v=edge[i].to ;
if(v!=f){
dfs1(v,u);
size[u]+=size[v];
if(size[v]>size[son[u]]) son[u]=v;
}
}
}
inline void dfs2(int u,int f)
{
dfn[u]=++tim;
dep[u]=dep[f]+1;
top[u]=(u==son[f]?top[f]:u);
wt[tim]=w[u];
if(son[u]!=0) dfs2(son[u],u);
for(int i=head[u];i;i=edge[i].nxt )
{
int v=edge[i].to ;
if(v!=f&&v!=son[u])
dfs2(v,u);
}
}
inline void build(int k,int l,int r)
{
if(l==r){
sum[k]=wt[l];
sum[k]%=mod;
return ;
}
int mid=(l+r)>>1;
build(k<<1,l,mid);
build(k<<1|1,mid+1,r);
sum[k]=(sum[k<<1]+sum[k<<1|1])%mod;
}
inline void pushdown(int k,int l,int r)
{
int mid=(l+r)>>1;
laz[k<<1]+=laz[k];
laz[k<<1|1]+=laz[k];
sum[k<<1]=(sum[k<<1]+laz[k]*(mid-l+1))%mod;
sum[k<<1|1]=(sum[k<<1|1]+laz[k]*(r-mid))%mod;
laz[k]=0;
}
long long query(int k,int l,int r,int x,int y)
{
if(x<=l&&r<=y) return sum[k]%mod;
int mid=(l+r)>>1;
long long res=0;
if(laz[k]!=0) pushdown(k,l,r);
if(x<=mid) res+=query(k<<1,l,mid,x,y);
if(mid<y) res+=query(k<<1|1,mid+1,r,x,y);
return res;
}
inline void modify(int k,int l,int r,int x,int y,int v)
{
if(x<=l&&r<=y)
{
laz[k]+=v;
sum[k]+=v*(r-l+1);
return ;
}
else
{
int mid=(l+r)>>1;
if(laz[k]!=0) pushdown(k,l,r);
if(x<=mid) modify(k<<1,l,mid,x,y,v);
if(mid<y) modify(k<<1|1,mid+1,r,x,y,v);
sum[k]=(sum[k<<1]+sum[k<<1|1])%mod;
}
}
inline void chrode(int x,int y,int v)
{
v%=mod;
while(top[x]!=top[y])
{
if(dep[top[x]]<dep[top[y]]) swap(x,y);
modify(1,1,n,dfn[top[x]],dfn[x],v);
x=fa[top[x]];
}
if(dep[x]>dep[y]) swap(x,y);
modify(1,1,n,dfn[x],dfn[y],v);
}
int qrode(int x,int y)
{
int ans=0;
while(top[x]!=top[y])
{
if(dep[top[x]]<dep[top[y]]) swap(x,y);
ans=(ans+query(1,1,n,dfn[top[x]],dfn[x]))%mod;
x=fa[top[x]];
}
if(dep[x]>dep[y]) swap(x,y);
ans=(ans+query(1,1,n,dfn[x],dfn[y]))%mod;
return ans%mod;
}
inline void chson(int x,int v)
{
modify(1,1,n,dfn[x],dfn[x]+size[x]-1,v);
}
int qson(int x)
{
return query(1,1,n,dfn[x],dfn[x]+size[x]-1)%mod;
}
int main()
{
n=read();m=read();r=read();mod=read();
for(int i=1;i<=n;i++) w[i]=read();
int k,x,y,z;
for(int i=1;i<n;i++){
x=read(),y=read();
addedge(x,y);
}
dfs1(r,0);
dfs2(r,0);
build(1,1,n);
for(int i=1;i<=m;i++){
k=read();
if(k==1){
x=read();y=read();z=read();
chrode(x,y,z);
}
if(k==2){
x=read();y=read();
printf("%d\n",qrode(x,y));
}
if(k==3){
x=read();z=read();
chson(x,z);
}
if(k==4){
x=read();
printf("%d\n",qson(x));
}
}
return 0;
}