已经把我脑子剖烂了.

严重怀疑我的子树修改查询.

#include<bits/stdc++.h>
using namespace std;
const int maxn=5e5+7;
int N,M,R,P,w[maxn],dep[maxn];
int head[maxn],nxt[maxn],to[maxn],cnt;//邻接表全家桶 
int Fa[maxn],Hd[maxn],Hson[maxn],SZ[maxn],id[maxn];
//树剖全家桶(爹,i的重链头,重儿子,子树大小,在线段树的位置 )
struct node{int l,r,dat,add;}tree[maxn];
void edge(int U,int V){
	nxt[++cnt]=head[U];to[cnt]=V;head[U]=cnt;
	nxt[++cnt]=head[V];to[cnt]=U;head[V]=cnt;
	return;
}
//以下为线段树 
int ls(int p){return p<<1;}
int rs(int p){return (p<<1)|1;}
int Len(int p){return tree[p].r-tree[p].l+1;} 
int Mid(int l,int r){return (l+r)>>1;}
void pushdown(int p){//懒标记
	if(tree[p].add){
		tree[ls(p)].add+=tree[p].add;
		tree[rs(p)].add+=tree[p].add;
		tree[ls(p)].dat+=tree[p].add*Len(ls(p));
		tree[rs(p)].dat+=tree[p].add*Len(rs(p));
		tree[ls(p)].dat%=P;tree[rs(p)].dat%=P; 
		tree[p].add=0;
	}
	return; 
}
void build(int l,int r,int p){//建树 
	tree[p].l=l;tree[p].r=r;
	if(l==r){tree[p].dat=w[l]%P;return;}
	int mid=Mid(l,r);
	build(l,mid,ls(p));build(mid+1,r,rs(p));
	tree[p].dat=(tree[ls(p)].dat+tree[rs(p)].dat)%P;
	return;
}
void change(int p,int l,int r,int k){
	if(l<=tree[p].l&&tree[p].r<=r){
		tree[p].dat+=1LL*k*Len(p);
		tree[p].dat%=P;
		tree[p].add+=k;
		tree[p].add%=P;
		return;
	}
	pushdown(p); 
	int mid=Mid(tree[p].l,tree[p].r);
	if(l<=mid)change(ls(p),l,r,k);
	if(r>mid)change(rs(p),l,r,k);
	tree[p].dat=(tree[ls(p)].dat+tree[rs(p)].dat)%P;
	return;
}
long long query(int p,int l,int r){
	if(l<=tree[p].l&&r>=tree[p].r)return tree[p].dat%P;
	pushdown(p);
	int mid=Mid(tree[p].l,tree[p].r);
	long long ret=0;
	if(l<=mid)ret+=query(ls(p),l,r);
	if(r>mid)ret+=query(rs(p),l,r);
	return ret%P;
}
//线段树部分结束 
//它 来 了
int dfs1(int u,int fa){
	int maxson=-1;
	SZ[u]=1;Fa[u]=fa;dep[u]=dep[fa]+1;
	for(int i=head[u];i;i=nxt[i]){
		int v=to[i];
		if(v==fa)continue;
		SZ[u]+=dfs1(v,u);
		if(SZ[v]>maxson)maxson=SZ[v],Hson[u]=v;
	}
	return SZ[u]; 
}
void dfs2(int u,int fa,int top){//当前节点,爹,重链头 
	id[u]=++cnt;Hd[u]=top;
	w[cnt]=w[u];
	if(!Hson[u])return;
	dfs2(Hson[u],u,top);
	for(int i=head[u];i;i=nxt[i])
		if(to[i]!=fa&&to[i]!=Hson[u])dfs2(to[i],u,to[i]);
	return;
}
void addTree(int u,int v,int W){
	W%=P;
	while(Hd[u]!=Hd[v]){
		if(dep[Hd[u]]<dep[Hd[v]])swap(u,v);
		change(1,id[Hd[u]],id[u],W);
		u=Fa[Hd[u]];
	}
	if(dep[u]>dep[v])swap(u,v);
	change(1,id[u],id[v],W);
	return;
}
int queryTree(int u,int v){
	int ret=0;
	while(Hd[u]!=Hd[v]){
		if(dep[Hd[u]]<dep[Hd[v]])swap(u,v);
		ret+=query(1,id[Hd[u]],id[u]);ret%=P;
		u=Fa[Hd[u]];
	}
	if(dep[u]>dep[v])swap(u,v);
	ret+=query(1,id[u],id[v]);
	return ret%P;
}
//E · N · D 
int main(){
	scanf("%d%d%d%d",&N,&M,&R,&P);
	for(int i=1;i<=N;i++)scanf("%d",&w[i]);
	for(int i=1;i<N;i++){int a,b;scanf("%d%d",&a,&b);edge(a,b);}
	cnt=0;
	dfs1(R,0);
	dfs2(R,0,R); 
	build(1,N,1);
	while(M--){
		//cout<<"Case "<<M+1<<endl;
		int op,x,y,z;
		scanf("%d",&op);
		if(op==1){
			//cout<<"修改\n";
			scanf("%d%d%d",&x,&y,&z);
			addTree(x,y,z);
		}else if(op==2){
			//cout<<"查询\n";
			scanf("%d%d",&x,&y);
			printf("%d\n",queryTree(x,y));
		}else if(op==3){
			//cout<<"修改\n";
			scanf("%d%d",&x,&y);
			change(1,id[x],id[x]+SZ[x]-1,y);
		}else{
			//cout<<"查询\n";
			scanf("%d",&x);
			printf("%d\n",query(1,id[x],id[x]+SZ[x]-1));
		}
	}
	return 0;
}