RT，在经过整个下午的调试之后，我已经快要崩溃了。

我对着神鱼的代码看了一遍又一遍，方法学了一遍又一遍，差不多都能背诵全文了，还是过不了，只有十分，555.

哪位好心人愿意帮忙看一下吗？谢谢。

#include<cstdio>
#include<iostream>
#define maxn1 100005
#define maxn2 200005
#define ll long long
using namespace std;
ll n,m,q,s,muxii,cnt=0;
ll sum1[maxn1],sum2[maxn1];
ll now[maxn1],before[maxn2],u[maxn2],v[maxn2],son[maxn1],depth[maxn1],fa[maxn1],size[maxn1],id[maxn1],top[maxn1],w[maxn1];
ll lowbit(ll x){
	return x&(-x);
}
void update(ll l,ll r,ll num){
	ll ad1=(l-1)*num%muxii;
	ll ad2=r*num%muxii;
	for(int t=l;t<=n;t+=lowbit(t)){
		sum1[t]+=num;
		sum1[t]%=muxii;
		sum2[t]+=ad1;
		sum2[t]%=muxii;
	}
	for(int t=r+1;t<=n;t+=lowbit(t)){
		sum1[t]-=num;
		sum1[t]%=muxii;
		sum2[t]-=ad2;
		sum2[t]%=muxii;
	}
	return;
}
ll querypoint(ll i){
	ll ans=0;
	for(int t=i;t>0;t-=lowbit(t)){
		ans+=sum1[t]*i-sum2[t];
		ans%=muxii;
	}
	return ans;
}
ll query(ll l,ll r){
	return querypoint(r)-querypoint(l-1);
}
void dfs1(ll x,ll f){
	fa[x]=f;
	size[x]=1;
	depth[x]=depth[f]+1;
	ll maxn=0;
	for(ll i=now[x];i!=-1;i=before[i]){
		if(v[i]==f)
			continue;
		dfs1(v[i],x);
		if(size[v[i]]>maxn){
			maxn=size[v[i]];
			son[x]=v[i];
		}
		size[x]+=size[v[i]];
	}
	return;
}
void dfs2(ll x,ll anc){
	top[x]=anc;
	id[x]=++cnt;
	if(w[x]!=0)
		update(id[x],id[x],w[x]);
	if(son[x]==0)
		return;
	dfs2(son[x],anc);
	for(ll i=now[x];i!=-1;i=before[i]){
		if(v[i]==fa[x]||v[i]==son[x])
			continue;
		dfs2(v[i],v[i]);
	} 
	return;
}
void updatepath(ll x,ll y,ll k){
	k%=muxii;
	while(top[x]!=top[y]){
		if(depth[top[x]]<depth[top[y]])
			swap(x,y);
		update(id[top[x]],id[x],k);
		x=fa[top[x]];
	}
	if(depth[x]>depth[y])
		swap(x,y);
	update(id[x],id[y],k);
	return;
}
ll querypath(ll x,ll y){
	ll ans=0;
	while(top[x]!=top[y]){
		if(depth[top[x]]<depth[top[y]])
			swap(x,y);
		ans+=query(id[top[x]],id[x]);
		ans=ans%muxii;
		x=fa[top[x]];
	}
	if(depth[x]>depth[y])
		swap(x,y);
	ans+=query(id[x],id[y]);
	ans=ans%muxii;
	return ans;
}
void updateson(ll x,ll k){
	k%=muxii;
	update(id[x],id[x]+size[x]-1,k);
	return;
}
ll queryson(ll x){
	return query(id[x],id[x]+size[x]-1);
}
ll t,x,y,z;
int main(){
	scanf("%lld%lld%lld%lld",&n,&q,&s,&muxii);
	m=n-1;
	for(ll i=1;i<=n;i++){
		scanf("%lld",&w[i]);
		now[i]=-1;
		son[i]=-1;
		depth[i]=0;
		fa[i]=-1;
		size[i]=0;
		id[i]=0;
		top[i]=-1;
	}
	for(ll i=1;i<=m;i++){
		scanf("%lld%lld",&u[i],&v[i]);
		before[i]=now[u[i]];
		now[u[i]]=i;
	}
	for(ll i=m+1;i<=2*m;i++){
		u[i]=v[i-m];
		v[i]=u[i-m];
		before[i]=now[u[i]];
		now[u[i]]=i;
	}
	dfs1(s,0);
	dfs2(s,s);
	while(q--){
		scanf("%lld",&t);
		if(t==1){
			scanf("%lld%lld%lld",&x,&y,&z);
			updatepath(x,y,z);
		}
		if(t==2){
			scanf("%lld%lld",&x,&y);
			printf("%lld\n",querypath(x,y)%muxii);
		}
		if(t==3){
			scanf("%lld%lld",&x,&z);
			updateson(x,z);
		}
		if(t==4){
			scanf("%lld",&x);
			printf("%lld\n",queryson(x)%muxii);
		}
	}
	return 0;
}