不知道为什么DFS1死循环了

#include<bits/stdc++.h>
using namespace std;
#define int long long
const int maxn=2e5+10;
int n,q,c[maxn],h[maxn*2],cnt,dyd[maxn],dydjl[maxn];
struct Edge
{
	int next,v,z;
}edge[maxn*2];
void addEdge(int u,int v,int z)
{
	edge[++cnt].z=z;
	edge[cnt].v=v;
	edge[cnt].next=h[u];
	h[u]=cnt;
}
int a[maxn],siz[maxn],nid[maxn],f[maxn],son[maxn],nt,deep[maxn],w[maxn],top[maxn],oid[maxn],jl[maxn];
void dfs1(int now,int fa,int sum)
{
	//cout<<"\n\n\n\n\n\n1111111111111111111111111111111111111111111111111111111111111\n\n\n\n\n\n\n";
	a[now]=c[now]-sum,f[now]=fa,siz[now]=1,deep[now]=deep[fa]+1,jl[now]+=jl[fa];
	int fl=0;
	for(int i=h[now];i;i=edge[i].next)
	{
		int y=edge[i].v;
		if(y==fa)continue;
		jl[y]+=edge[i].z;
		dfs1(y,now,sum+edge[i].z*2);
		siz[now]+=siz[y];
		if(siz[y]>fl)
		{
			fl=siz[y];
			son[now]=y;
		}
	}
	return ;
}
void dfs2(int x,int root)
{
	//cout<<x<<"  00\n";
	nid[x]=++nt,w[nt]=a[x],top[x]=root;
	oid[nt]=x;
	if(son[x]==0)return ;
	dfs2(son[x],root);
	for(int i=h[x];i;i=edge[i].next)
	{
		int y=edge[i].v;
		if(y==f[x]||y==son[x])continue;
		dfs2(y,y);
	}
}
struct Tree
{
	int l,r,lazy,zdid,zd;
}t[maxn<<2];
struct Tree1
{
	int l,r,zd1,zd2;
}t1[maxn<<2];
struct node
{
	int x,id;
};
void pushup(int id)
{
	t[id].zd=max(t[id*2].zd,t[id*2+1].zd);
	if(t[id*2].zd>t[id*2+1].zd)t[id].zdid=t[id*2].zdid;
	else t[id].zdid=t[id*2+1].zdid;
	return ;
}
void pushdown(int id)
{
	if(t[id].lazy)
	{
		t[id*2].lazy+=t[id].lazy;
		t[id*2+1].lazy+=t[id].lazy;
		t[id*2].zd+=t[id].lazy;
		t[id*2+1].zd+=t[id].lazy;
		t[id].lazy=0;
	}
	return ;
}
void buildtree(int id,int l,int r)
{
	t[id].l=l,t[id].r=r;
	if(l==r)
	{
		t[id].zd=w[l];
		t[id].zdid=l;
		return ;
	}
	int mid=(l+r)/2;
	buildtree(id*2,l,mid);
	buildtree(id*2+1,mid+1,r);
	pushup(id);
}
void modify(int id,int l,int r,int z)
{
	if(t[id].l>=l&&t[id].r<=r)
	{
		t[id].lazy+=z;
		t[id].zd+=z;
		return ;
	}
	pushdown(id);
	int mid=(t[id].l+t[id].r)/2;
	if(mid>=l)modify(id*2,l,r,z);
	if(mid<r)modify(id*2+1,l,r,z);
	pushup(id);
	return ;
}
node query(int id,int l,int r)
{
	if(t[id].l>=l&&t[id].r<=r)
	{
		return (node){t[id].zd,t[id].zdid};
	}
	pushdown(id);
	int mid=(t[id].l+t[id].r)/2,L=-1000000000,R=-1000000000;
	if(mid>=l)L=query(id*2,l,r).x;
	if(mid<r)R=query(id*2+1,l,r).x;
	pushup(id);
	if(L>=R)return (node){L,t[id*2].zdid};
	else return (node){R,t[id*2+1].zdid};
}
void dfs3(int x)
{	
	//cout<<x<<": \n";
	node gh=query(1,1,n);
	//for(int i=1;i<=n;i++)cout<<query(1,nid[i],nid[i]).x<<" ";
	//cout<<oid[gh.id];
	//cout<<"\n";
	dyd[x]=oid[gh.id];
	dydjl[x]=gh.x;
	//cout<<x<<" "<<gh.x<<"\n";
	for(int i=h[x];i;i=edge[i].next)
	{
		int y=edge[i].v;
		if(y==f[x])continue;
		//cout<<"edge[i].z "<<edge[i].z<<"\n";
		modify(1,1,n,-edge[i].z*2);
		modify(1,nid[y],nid[y]+siz[y]-1,edge[i].z*4);
		dfs3(y);
		modify(1,1,n,edge[i].z*2);
		modify(1,nid[y],nid[y]+siz[y]-1,-edge[i].z*4);
	}
}
void pushup1(int id)
{
	t1[id].zd1=max(t1[id*2].zd1,t1[id*2+1].zd1);
	t1[id].zd2=max(t1[id*2].zd2,t1[id*2+1].zd2);
	return ;
}
void buildtree1(int id,int l,int r)
{
	t1[id].l=l,t1[id].r=r;
	if(l==r)
	{
		t1[id].zd1=c[nid[l]];
		//int x=oid[l],y=dyd[x];
		t1[id].zd2=dydjl[oid[l]];
		return ;
	}
	int mid=(t1[id].l+t1[id].r)/2;
	buildtree1(id*2,l,mid);
	buildtree1(id*2+1,mid+1,r);
	pushup1(id);
	return ;
}
int query1(int id,int l,int r)
{
	if(t1[id].l>=l&&t1[id].r<=r)
	{
		return t1[id].zd1;
	}
	int mid=(t1[id].l+t1[id].r)/2,sum=-1000000000;
	if(mid>=l)sum=max(sum,query1(id*2,l,r));
	if(mid<r)sum=max(sum,query1(id*2+1,l,r));
	return sum;
}
int query2(int id,int l,int r)
{
	if(t1[id].l>=l&&t1[id].r<=r)
	{
		return t1[id].zd2;
	}
	int mid=(t1[id].l+t1[id].r)/2,sum=-1000000000;
	if(mid>=l)sum=max(sum,query2(id*2,l,r));
	if(mid<r)sum=max(sum,query2(id*2+1,l,r));
	return sum;
}
int ans1,ans2;
int lca(int x,int y)
{
	while(top[x]!=top[y])
	{
		if(deep[top[x]]<deep[top[x]])swap(x,y);
		ans1=max(ans1,query1(1,nid[top[x]],nid[x]));
		ans2=max(ans2,query2(1,nid[top[x]],nid[x]));
		x=f[top[x]];
	}
	if(deep[x]>deep[y])swap(x,y);
	ans1=max(ans1,query1(1,nid[x],nid[y]));
	ans2=max(ans2,query2(1,nid[x],nid[y]));
	return x;
}
signed main()
{
	//freopen("1.out","w",stdout);
	cin>>n>>q;
	for(int i=1;i<=n;i++)cin>>c[i];
	for(int i=1;i<n;i++)
	{
		int u,v,z;
		cin>>u>>v>>z;
		addEdge(u,v,z);
		addEdge(v,u,z);
	}
	
	dfs1(1,0,0);
	
	dfs2(1,1);
	
	buildtree(1,1,n);
	buildtree1(1,1,n);
	dfs3(1);
	//for(int i=1;i<=n;i++)cout<<dyd[i]<<" ";
	//cout<<"\n";
	
	//dfs
	//for(int i=1;i<=n;i++)cout<<query1(1,nid[i],nid[i])<<" "<<query2(1,nid[i],nid[i])<<"\n";
	//cout<<"\n";
	
	while(q--)
	{
		int x,y;
		cin>>x>>y;
		ans1=-100000000,ans2=-1000000000;
		int fxy=lca(x,y);
		//cout<<fxy<<"\n";
		//cout<<ans1<<" "<<ans2<<" "<<c[x]+c[y]-(jl[x]+jl[y]-2*jl[fxy])<<"\n";
		cout<<max(ans1,ans2)+c[x]+c[y]-(jl[x]+jl[y]-2*jl[fxy])<<"\n";
	}
	
	return 0;
}