洛谷 P3384树链剖分 题解

#include <bits/stdc++.h>
using namespace std;
int n,m,r,p;
int head[2000010],cnt;
class littlestar{
	public:
		int to;
		int nxt;
		void add(int u,int v){
			to=v;
			nxt=head[u];
			head[u]=cnt;		
		}
}star[2000010];
int a[100010];
int f[100010],dep[100010],son[100010],seg[100010],rev[100010],size[100010],top[100010];
void dfs1(int u,int fa)
{
	size[u]=1;
	f[u]=fa;
	dep[u]=dep[fa]+1;
	for(int i=head[u];i;i=star[i].nxt){
		int v=star[i].to;
		if(v==fa) continue;
		dfs1(v,u);
		size[u]+=size[v];
		if(size[v]>size[son[u]]) son[u]=v;
	}
}
void dfs2(int u,int fa)
{
	if(son[u]){
		seg[son[u]]=++seg[0];
		rev[seg[0]]=son[u];
		top[son[u]]=top[u];
		dfs2(son[u],u);
	}
	for(int i=head[u];i;i=star[i].nxt){
		int v=star[i].to;
		if(v==fa) continue;
		if(!top[v]){
			seg[v]=++seg[0];
			rev[seg[0]]=v;
			top[v]=v;
			dfs2(v,u);
		}
	}
}
struct ss{
	int sum;
	int lazy;
}tree[1000010];
void build(int k,int l,int r)
{
	if(l==r){
		tree[k].sum=a[rev[l]]%p;
		return;
	}
	int mid=(l+r)/2;
	build(k<<1,l,mid);
	build(k<<1|1,mid+1,r);
	tree[k].sum=tree[k<<1].sum+tree[k<<1|1].sum;
}
void pre()
{
	dfs1(r,0);
	seg[0]=seg[r]=1;
	top[r]=r;
	rev[1]=r;
	dfs2(r,0);
	build(1,1,seg[0]);	
}
void pushdown(int k,int l,int r)
{
	int mid=(l+r)/2;
	tree[k<<1].lazy=(tree[k<<1].lazy+tree[k].lazy)%p;
	tree[k<<1].sum=(tree[k<<1].sum+tree[k].lazy*(mid-l+1))%p;
	tree[k<<1|1].lazy=(tree[k<<1|1].lazy+tree[k].lazy)%p;
	tree[k<<1|1].sum=(tree[k<<1|1].sum+tree[k].lazy*(r-mid))%p;
	tree[k].lazy=0;
}
int query(int k,int l,int r,int x,int y)
{
	if(r<x||l>y){
		return 0;
	}
	if(l>=x&&r<=y){
		return tree[k].sum%p;
	}
	int mid=(l+r)/2;
	pushdown(k,l,r);
	return (query(k<<1,l,mid,x,y)+query(k<<1|1,mid+1,r,x,y))%p;
}
void change(int k,int l,int r,int x,int y,int goal)
{
	if(r<x||l>y) return;
	if(l>=x&&r<=y){
		tree[k].sum=(tree[k].sum+(r-l+1)*goal)%p;
		tree[k].lazy=(tree[k].lazy+goal)%p;
		return;
	}
	pushdown(k,l,r);
	int mid=(l+r)/2;
	change(k<<1,l,mid,x,y,goal);
	change(k<<1|1,mid+1,r,x,y,goal);
	tree[k].sum=(tree[k<<1].sum+tree[k<<1|1].sum)%p;
}
void changeroad(int x,int y,int z)
{
	int fx=top[x],fy=top[y];
	while(fx!=fy){
		if(dep[fx]<dep[fy]) swap(fx,fy),swap(x,y);
		change(1,1,seg[0],seg[fx],seg[x],z);
		x=f[fx];
		fx=top[x];
	}
	if(dep[x]>dep[y]) swap(x,y);
	change(1,1,seg[0],seg[x],seg[y],z);
}
int queryroad(int x,int y)
{
	long long ans=0;
	int fx=top[x],fy=top[y];
	while(fx!=fy){
		if(dep[fx]<dep[fy]) swap(fx,fy),swap(x,y);
		ans=(ans+query(1,1,seg[0],seg[fx],seg[x]))%p;
		x=f[fx];
		fx=top[x];
	}
	if(dep[y]<dep[x]) swap(x,y);
	ans=(ans+query(1,1,seg[0],seg[x],seg[y]))%p;
	return ans%p;
}
void changetree(int x,int goal)
{
	change(1,1,seg[0],seg[x],seg[x]+size[x]-1,goal);
	return;
}
long long querytree(int x)
{
	long long res=0;
	res=(res+query(1,1,seg[0],seg[x],seg[x]+size[x]-1))%p;
	return res;
}
int main(){
	cin>>n>>m>>r>>p;
	for(int i=1;i<=n;i++){
		scanf("%d",&a[i]);
	}
	for(int i=1;i<=n-1;i++){
		int u,v;
		scanf("%d%d",&u,&v);
		star[++cnt].add(u,v);
		star[++cnt].add(v,u);
	}
	pre();
	for(int i=1;i<=m;i++){
		int type;
		scanf("%d",&type);
		if(type==1){
			int x,y,z;
			scanf("%d%d%d",&x,&y,&z);
			changeroad(x,y,z);
		}
		else if(type==2){
			int x,y;
			scanf("%d%d",&x,&y);
			cout<<queryroad(x,y)%p<<endl;
		}
		else if(type==3){
			int x,z;
			scanf("%d%d",&x,&z);
			changetree(x,z);
		}
		else{
			int x;
			scanf("%d",&x);
			cout<<querytree(x)%p<<endl;
		}
	}
}
/*
5 5 2 30000
7 3 7 8 0 
1 2
1 5
3 1
4 1
3 4 2
3 2 2
4 5
1 5 1 3
2 1 3
*/