codevs 3305 水果姐逛水果街Ⅱ

/*我尼玛 又一个min打成max 看了半天....*/
#include<iostream>
#include<cstdio>
#include<cstring>
#define maxn 200010
#define inf 0x7fffffff
using namespace std;
int n,m,head[maxn],num,v[maxn],fa[maxn][25],c[maxn];
int mii[maxn][25],mxx[maxn][25],up[maxn][25],down[maxn][25];
struct node{
int v,pre;
}e[maxn*2];
int init(){
int x=0;char s=getchar();
while(s<'0'||s>'9')s=getchar();
while(s>='0'&&s<='9'){x=x*10+s-'0';s=getchar();}
return x;
}
void Add(int from,int to){
num++;e[num].v=to;
e[num].pre=head[from];
head[from]=num;
}
void Dfs(int now,int from,int dep,int val){
fa[now][0]=from;c[now]=dep;
mii[now][0]=min(val,v[now]);
mxx[now][0]=max(val,v[now]);
up[now][0]=max(0,v[from]-v[now]);
down[now][0]=max(0,v[now]-v[from]);
for(int i=head[now];i;i=e[i].pre){
if(e[i].v==from)continue;
Dfs(e[i].v,now,dep+1,v[now]);
}
}
void Get_fa(){
for(int j=1;j<=20;j++)
for(int i=1;i<=n;i++){
fa[i][j]=fa[fa[i][j-1]][j-1];
mii[i][j]=min(mii[i][j-1],mii[fa[i][j-1]][j-1]);
mxx[i][j]=max(mxx[i][j-1],mxx[fa[i][j-1]][j-1]);
up[i][j]=max(up[i][j-1],up[fa[i][j-1]][j-1]);
up[i][j]=max(up[i][j],mxx[fa[i][j-1]][j-1]-mii[i][j-1]);
down[i][j]=max(down[i][j-1],down[fa[i][j-1]][j-1]);
down[i][j]=max(down[i][j],mxx[i][j-1]-mii[fa[i][j-1]][j-1]);
}
}
int LCA(int a,int b){
if(c[a]<c[b])swap(a,b);
int t=c[a]-c[b];
for(int i=0;i<=20;i++)
if((1<<i)&t)a=fa[a][i];
if(a==b)return a;
for(int i=20;i>=0;i--)
if(fa[a][i]!=fa[b][i]){
a=fa[a][i];
b=fa[b][i];
}
return fa[a][0];
}
int Up_lca(int a,int b){
int t=c[a]-c[b],ret=0,minner=inf;
for(int i=0;i<=20;i++)
if((1<<i)&t){
ret=max(ret,up[a][i]);
ret=max(ret,mxx[a][i]-minner);
minner=min(minner,mii[a][i]);
a=fa[a][i];
}
return ret;
}
int Down_lca(int a,int b){
int t=c[a]-c[b],ret=0,maxxer=0;
for(int i=0;i<=20;i++)
if((1<<i)&t){
ret=max(ret,down[a][i]);
ret=max(ret,maxxer-mii[a][i]);
maxxer=max(maxxer,mxx[a][i]);
a=fa[a][i];
}
return ret;
}
int Query_max(int a,int b){
int t=c[a]-c[b],maxxer=v[a];
for(int i=0;i<=20;i++)
if((1<<i)&t){
maxxer=max(maxxer,mxx[a][i]);
a=fa[a][i];
}
return maxxer;
}
int Query_min(int a,int b){
int t=c[a]-c[b],minner=v[a];
for(int i=0;i<=20;i++)
if((1<<i)&t){
minner=min(minner,mii[a][i]);
a=fa[a][i];
}
return minner;
}
int main()
{
n=init();
for(int i=1;i<=n;i++)
v[i]=init();
int u,v;
for(int i=1;i<n;i++){
u=init();v=init();
Add(u,v);Add(v,u);
}
memset(mii,127,sizeof(mii));
Dfs(1,0,0,0);Get_fa();
m=init();
while(m--){
u=init();v=init();
int anc=LCA(u,v);
//printf("%d\n",anc);
int ans=0;
ans=max(Up_lca(u,anc),Down_lca(v,anc));
ans=max(ans,Query_max(v,anc)-Query_min(u,anc));
printf("%d\n",ans);
}
return 0;
}