用的vector，是只能用链式前向星吗

#include<bits/stdc++.h>
#define ll long long
#define debug printf("ciallo\n")
#define rep(i,aaa,bbb) for(int i=(aaa);i<=(bbb);i++)
#define per(i,aaa,bbb) for(int i=(aaa);i>=(bbb);i--)
#define pb push_back
#define mid ((l+r)>>1)
#define lson x<<1,l,mid
#define rson x<<1|1,mid+1,r
#define len (r-l+1)
using namespace std;

int read(){
	int f=1,x=0;
	char c=getchar();
	while(c>'9'||c<'0'){
		if(c=='-') f=-1;
		c=getchar();
	}
	while(c>='0'&&c<='9'){
		x=(x<<1)+(x<<3)+(c^48);
		c=getchar();
	}
	return x*f;
}

const int inf=0x7fffffff;
const int maxn=1e5+10;

int n,m,root,mod;
int w[maxn],cnt;
vector<int>t[maxn];
int dep[maxn],fa[maxn],size[maxn],son[maxn],top[maxn];//true index
int id[maxn],wt[maxn];//index in T,using Tfunction need id[x]
//xds------------------------------------
struct node{
	int x,add;
}T[maxn<<2];

void build(int x,int l,int r){
	if(l==r){
		T[x].x=wt[l];
		return;
	}
	build(lson);
	build(rson);
}

inline void down(int x,int l,int r){
	if(T[x].add==0)return;
	T[x<<1].add+=T[x].add;
	T[x<<1|1].add+=T[x].add;
	T[x].x+=T[x].add*len;
	T[x].x%=mod;
	T[x<<1].add%=mod;
	T[x<<1|1].add%=mod;
	T[x].add=0;
}

void rewrite(int x,int l,int r,int lq,int rq,int vl){
	if(l>=lq&&r<=rq){
		T[x].add=(T[x].add+vl)%mod;
	}
	down(x,l,r);
	if(lq<=mid)rewrite(lson,lq,rq,vl);
	if(rq>mid)rewrite(rson,lq,rq,vl);
}

int count(int x,int l,int r,int lq,int rq){
	if(l!=r)down(x,l,r);
	if(l>=lq&&r<=rq)return T[x].x;
	ll ccc=0;
	if(lq<=mid)ccc+=count(lson,lq,rq);
	ccc%=mod;
	if(rq>mid)ccc+=count(rson,lq,rq);
	return ccc%mod;
}
//---------------------------------------
void dfs1(int x,int f,int deep){
	dep[x]=deep;
	fa[x]=f;
	int mmm=-1;
	for(int i:t[x]){
		if(i!=f){
			dfs1(i,x,deep+1);
			size[x]+=size[i];
			if(size[i]>mmm)mmm=size[i],son[x]=i;
		}
	}
}

void dfs2(int x,int f){
	id[x]=++cnt;
	wt[cnt]=wt[x];
	top[x]=f;
	if(!son[x])return;
	dfs2(son[x],f);
	for(int i:t[x]){
		if(i!=fa[x]&&i!=son[x]){
			dfs2(i,i);
		}
	}
}

inline void q1(int x,int y,int z){
	z%=mod;
	while(top[x]!=top[y]){
		if(dep[top[x]]<dep[top[y]])swap(x,y);
		rewrite(1,1,n,id[top[x]],id[x],z);
		x=fa[top[x]];
	}
	if(dep[x]<dep[y])swap(x,y);
	rewrite(1,1,n,id[y],id[x],z);
}

inline int q2(int x,int y){
	ll ans=0;
	while(top[x]!=top[y]){
		if(dep[top[x]]<dep[top[y]])swap(x,y);
		ans=(ans+count(1,1,n,id[top[x]],id[x]))%mod;
		x=fa[top[x]];
	}
	if(dep[x]<dep[y])swap(x,y);
	return (ans+count(1,1,n,id[y],id[x]))%mod;
}

inline void q3(int x,int z){
	rewrite(1,1,n,id[x],id[x]+size[x]-1,z);
}

inline int q4(int x){
	return count(1,1,n,id[x],id[x]+size[x]-1);
}

int main(){
	n=read(),m=read(),root=read(),mod=read();
	rep(i,1,n)w[i]=read()%mod;
	rep(i,2,n){
		int u=read(),v=read();
		t[u].pb(v),t[v].pb(u);
	}
	dfs1(root,0,0);
	dfs2(root,0);
	build(1,1,n);
	while(m--){
		int k=read();
		if(k==1){
			int x=read(),y=read(),z=read();
			q1(x,y,z);
		}
		if(k==2){
			int x=read(),y=read();
			printf("%d\n",q2(x,y));
		}
		if(k==3){
			int x=read(),z=read();
			q3(x,z);
		}
		if(k==4){
			int x=read();
			printf("%d\n",q4(x));
		}
	}
	return 0;
}