只有$3$个点AC，剩下全RE，数组开大了也没用。

#include<cstdio>
#include<vector>
using namespace std;
#define LE(x) (x<<1)
#define RT(x) (x<<1|1)
int n;
long long p;
inline long long mod(long long x)
{
	return x<p?x:x-p;
}
long long w[100001];
vector<int>g[100001];
inline void addedge(int u,int v)
{
	g[u].push_back(v);
	g[v].push_back(u);
}
int deep[100001],f[100001],size[100001],son[100001],top[100001],id[100001],tot,rank[100001];
void dfs1(int now,int fa)
{
	deep[now]=deep[fa]+1;
	f[now]=fa;
	size[now]=1;
	for (int i=0;i<g[now].size();++i)
	{
		int u=g[now][i];
		if	(u!=fa)
		{
			dfs1(u,now);
			size[now]+=size[u];
			if	(size[u]>size[son[now]])	son[now]=u;
		}
	}
}
void dfs2(int now,int anc)
{
	top[now]=anc;
	id[now]=++tot;
	rank[tot]=now;
	if	(!son[now])	return;
	dfs2(son[now],anc);
	for (int i=0;i<g[now].size();++i)
	{
		int u=g[now][i];
		if	(u!=f[now]&&u!=son[now])	dfs2(u,u);
	}
}
long long sumv[400000],addv[400000];
inline void push_up(int x)
{
	sumv[x]=mod(sumv[LE(x)]+sumv[RT(x)]);
}
void build(int x,int l,int r)
{
	if	(l==r)
	{
		sumv[x]=w[rank[l]];
		return;
	}
	int mid=l+r>>1;
	build(LE(x),l,mid);
	build(RT(x),mid+1,r);
	push_up(x);
}
void push_down(int x,int l,int r)
{
	if	(addv[x])
	{
		addv[LE(x)]=mod(addv[LE(x)]+addv[x]);
		addv[RT(x)]=mod(addv[RT(x)]+addv[x]);
		int mid=l+r>>1;
		sumv[LE(x)]=(sumv[LE(x)]+addv[x]*(mid-l+1))%p;
		sumv[RT(x)]=(sumv[RT(x)]+addv[x]*(r-mid))%p;
		addv[x]=0;
	}
}
void optadd(int x,int l,int r,int ql,int qr,int k)
{
	if	(ql<=l&&r<=qr)
	{
		addv[x]=mod(addv[x]+k);
		sumv[x]=(sumv[x]+(r-l+1)*k)%p;
		return;
	}
	int mid=l+r>>1;
	push_down(x,l,r);
	if	(ql<=mid)	optadd(LE(x),l,mid,ql,qr,k);
	if	(qr>mid)	optadd(RT(x),mid+1,r,ql,qr,k);
	push_up(x);
}
long long querysum(int x,int l,int r,int ql,int qr)
{
	if	(ql<=l&&r<=qr)	return sumv[x];
	int mid=l+r>>1;
	long long ans=0;
	push_down(x,l,r);
	if	(ql<=mid)	ans=mod(ans+querysum(LE(x),l,mid,ql,qr));
	if	(qr>mid)	ans=mod(ans+querysum(RT(x),mid+1,r,ql,qr));
	return ans;
}
void update(int x,int y,int z)
{
	while (top[x]!=top[y])
	{
		if	(deep[x]>=deep[y])
		{
			optadd(1,1,n,id[top[x]],id[x],z);
			x=f[top[x]];
		}
		else
		{
			optadd(1,1,n,id[top[y]],id[y],z);
			y=f[top[y]];
		}
	}
	if	(id[x]<id[y])	optadd(1,1,n,id[x],id[y],z);
	else	optadd(1,1,n,id[y],id[x],z);
}
long long query(int x,int y)
{
	long long ans=0;
	while (top[x]!=top[y])
	{
		if	(deep[x]>=deep[y])
		{
			ans=mod(ans+querysum(1,1,n,id[top[x]],id[x]));
			x=f[top[x]];
		}
		else
		{
			ans=mod(ans+querysum(1,1,n,id[top[y]],id[y]));
			y=f[top[y]];
		}
	}
	if	(id[x]<id[y])	ans=mod(ans+querysum(1,1,n,id[x],id[y]));
	else	ans=mod(ans+querysum(1,1,n,id[y],id[x]));
	return ans;
}
int main()
{
	int m,r;
	scanf("%d%d%d%lld",&n,&m,&r,&p);
	for (int i=1;i<=n;++i)
	{
		scanf("%lld",&w[i]);
		w[i]%=p;
	}
	int u,v;
	for (int i=1;i<n;++i)
	{
		scanf("%d%d",&u,&v);
		addedge(u,v);
	}
	dfs1(r,0);
	dfs2(r,r);
	build(1,1,n);
	int opt,x,y,z;
	for (int i=1;i<=m;++i)
	{
		scanf("%d%d",&opt,&x);
		switch(opt)
		{
			case 1:
			scanf("%d%d",&y,&z);
			update(x,y,z);
			break;
			case 2:
			scanf("%d",&y);
			printf("%lld\n",query(x,y));
			break;
			case 3:
			scanf("%d",&z);
			optadd(1,1,n,id[x],id[x]+size[x]-1,z);
			break;
			case 4:printf("%lld\n",querysum(1,1,n,id[x],id[x]+size[x]-1));break;
		}
	}
	return 0;
}

PS：感觉像是dfs1的问题。