{"id":120,"date":"2010-02-22T19:48:00","date_gmt":"2010-02-22T11:48:00","guid":{"rendered":"http:\/\/localhost\/?p=120"},"modified":"2010-02-22T19:48:00","modified_gmt":"2010-02-22T11:48:00","slug":"pku_3728_the_merchant","status":"publish","type":"post","link":"https:\/\/www.shuizilong.com\/wjmzbmr\/?p=120","title":{"rendered":"PKU 3728 The merchant"},"content":{"rendered":"

Link\uff1a\u9898\u76ee<\/a>
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\u800cTarjan\u662f\u7ebf\u6027\u7684\u3002\u3002
\u8fd9\u9053\u9898\u76ee\u5c31\u662f\u8bf4\u7ed9\u4f60\u4e00\u4e2a\u9897\u8fb9\u4e0d\u4ee3\u6743\uff0c\u70b9\u4ee3\u6743\u7684\u6811\uff0c\u6709\u4e2a\u5546\u4eba\u8981\u65c5\u884c\u3002\u6bcf\u6b21\u4ece\u4e00\u4e2a\u70b9\u5230\u53e6\u4e00\u4e2a\u70b9\uff0c\u70b9\u6743\u8868\u793a\u5546\u54c1\u7684\u4ef7\u683c\u3002\u3002\u5546\u4eba\u6700\u591a\u8fdb\u8d27\u548c\u5356\u51fa\u4e00\u6b21\uff0c\u6c42\u4ed6\u7684\u6700\u5927\u6536\u5165(\u53ef\u4ee5\u4e0d\u4ea4\u6613)\u3002\u3002
\u8fd9\u9053\u9898\u5c31\u9700\u8981\u7ef4\u62a4\u4e00\u4e2a\u5e76\u67e5\u96c6\u4e2d\u9876\u70b9\u5230\u5e76\u67e5\u96c6\u4e2d\u7236\u4eb2\u7684\u8def\u5f84\u76844\u4e2a\u503c\u4e86\uff0c\u6700\u5927\u70b9\u6743\uff0c\u6700\u5c0f\u70b9\u6743\uff0c\u4ece\u5b83\u5230\u5e76\u67e5\u96c6\u4e2d\u7236\u4eb2\u4e00\u8def\u7684\u6700\u5927\u6536\u5165\uff0c\u4ece\u5e76\u67e5\u96c6\u7236\u4eb2\u5230\u5b83\u4e00\u8def\u7684\u6700\u5927\u6536\u5165\u3002\u3002
\u8fd9\u662f\u53ef\u4ee5\u5408\u5e76\u7684\u3002\u3002\u7136\u540e\u6c42\u7684\u65f6\u5019\u3002\u3002\u7ec8\u70b9\u5230lca\u7684\u4fe1\u606f\u8981\u53cd\u4e00\u4e0b\u3002\u3002
Code\uff1a

#include<cstdio>
#include<vector>
#include<algorithm>
#include<iostream>
#define pb push_back
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
const int inf=1<<20;
const int maxn=50000;int n;
const int maxm=maxn;int m;
struct edge
{
int t;
edge(int _t):t(_t){}
};
struct queryLca
{
bool s;
int t,n;
queryLca(int _t,int _n,bool _s):t(_t),n(_n),s(_s){}
};
struct query
{
int a,b,n;
query(int _a,int _b,int _n):a(_a),b(_b),n(_n){}
};
struct info
{
int Min,Max,Pro,RPro;
info(int v=0):Min(v),Max(v),Pro(0),RPro(0){}
info R()
{
info ans=*this;
swap(ans.Pro,ans.RPro);
return ans;
}
void Merge(const info& o)
{
Pro=max(Pro,o.Pro);
Pro=max(Pro,o.Max-Min);
RPro=max(RPro,o.RPro);
RPro=max(RPro,Max-o.Min);
Min=min(Min,o.Min);
Max=max(Max,o.Max);
}
};
vector<edge> E[maxn];
vector<queryLca> Lca[maxn];
vector<query> Query[maxn];
typedef vector<edge>::iterator eit;
typedef vector<queryLca>::iterator lit;
typedef vector<query>::iterator qit;
info Ans[maxm];
void add_edge(int s,int t)
{
E[s].pb(edge(t));
E[t].pb(edge(s));
}
void add_lca(int s,int t,int n)
{
Lca[s].pb(queryLca(t,n,true));
Lca[t].pb(queryLca(s,n,false));
}
info P[maxn];
int F[maxn];
void set()
{
rep(i,n) F[i]=i;
}
int find(int x)
{
int tmp=F[x];
if(F[x]!=x)
F[x]=find(F[x]),P[x].Merge(P[tmp]);
return F[x];
}
void Union(int i,int j)
{
F[j]=i;
}
bool vis[maxn]={0};
void dfs(int x)
{
vis[x]=true;
for(eit i=E[x].begin();i!=E[x].end();i++)if(!vis[i->t])
dfs(i->t),Union(x,i->t);
for(lit i=Lca[x].begin();i!=Lca[x].end();i++)
{
if(vis[i->t])
{
if(i->s)
Query[find(i->t)].pb(query(x,i->t,i->n));
else
Query[find(i->t)].pb(query(i->t,x,i->n));
}
}
for(qit i=Query[x].begin();i!=Query[x].end();i++)
{
find(i->a);find(i->b);
info&t=Ans[i->n];
t=P[i->a];t.Merge(P[i->b].R());
}
}
void init()
{
scanf("%d",&n);int s,t,c;
set();
for(int i=0;i<n;i++)
scanf("%d",&c),P[i]=info(c);
for(int i=0;i<n-1;i++)
{
scanf("%d %d",&s,&t);
add_edge(s-1,t-1);
}
scanf("%d",&m);int a,b;
for(int i=0;i<m;i++)
{
scanf("%d %d",&a,&b);
add_lca(a-1,b-1,i);
}
}
void solve()
{
dfs(0);
for(int i=0;i<m;i++)
printf("%dn",Ans[i].Pro);
}
int main()
{
\/\/freopen("in","r",stdin);
\/\/freopen("out","w",stdout);
init();
solve();
}<\/strong><\/em>
\u672c\u9ad8\u4eae\u4ee3\u7801\u4f7f\u7528codeHl\u751f\u6210\uff0c <\/p>\n","protected":false},"excerpt":{"rendered":"

Link\uff1a\u9898\u76ee\u5c31\u662f\u8bf4\u4e0a\u6b21\u6211\u8bf4\u7684\u90a3\u4e2aPKU\u6708\u8d5b\u9898\u3002\u3002Tarjan\u79bb\u7ebf\u5c31\u662fNB\u554a\u3002\u3002\u90a3\u4e2a\u4fdd\u5b582\u7684\u4e58\u65b9\u7684\u65e2\u8017\u7a7a\u95f4\uff0c\u53c8\u8017\u65f6\u95f4\u3002\u3002\u800cTarjan\u662f\u7ebf\u6027\u7684\u3002\u3002\u8fd9\u9053\u9898\u76ee\u5c31\u662f\u8bf4\u7ed9\u4f60\u4e00\u4e2a\u9897\u8fb9\u4e0d\u4ee3\u6743\uff0c\u70b9\u4ee3\u6743\u7684\u6811\uff0c\u6709\u4e2a\u5546\u4eba\u8981\u65c5\u884c\u3002\u6bcf\u6b21\u4ece\u4e00\u4e2a\u70b9\u5230\u53e6\u4e00\u4e2a\u70b9\uff0c\u70b9\u6743\u8868\u793a\u5546\u54c1\u7684\u4ef7\u683c\u3002\u3002\u5546\u4eba\u6700\u591a\u8fdb\u8d27\u548c\u5356\u51fa\u4e00\u6b21\uff0c\u6c42\u4ed6\u7684\u6700\u5927\u6536\u5165(\u53ef\u4ee5\u4e0d\u4ea4\u6613)\u3002\u3002\u8fd9\u9053\u9898\u5c31\u9700\u8981\u7ef4\u62a4\u4e00\u4e2a\u5e76\u67e5\u96c6\u4e2d\u9876\u70b9\u5230\u5e76\u67e5\u96c6\u4e2d\u7236\u4eb2\u7684\u8def\u5f84\u76844\u4e2a\u503c\u4e86\uff0c\u6700\u5927\u70b9\u6743\uff0c\u6700\u5c0f\u70b9\u6743\uff0c\u4ece\u5b83\u5230\u5e76\u67e5\u96c6\u4e2d\u7236\u4eb2\u4e00\u8def\u7684\u6700\u5927\u6536\u5165\uff0c\u4ece\u5e76\u67e5\u96c6\u7236\u4eb2\u5230\u5b83\u4e00\u8def\u7684\u6700\u5927\u6536\u5165\u3002\u3002\u8fd9\u662f\u53ef\u4ee5\u5408\u5e76\u7684\u3002\u3002\u7136\u540e\u6c42\u7684\u65f6\u5019\u3002\u3002\u7ec8\u70b9\u5230lca\u7684\u4fe1\u606f\u8981\u53cd\u4e00\u4e0b\u3002\u3002Code\uff1a#include<cstdio>#include<vector>#include<algorithm>#include<iostream>#define pb push_back#define rep(i,n) for(int i=0;i<n;i++)using namespace std;const int inf=1<<20;const int maxn=50000;int n;const int maxm=maxn;int m;struct edge{ int t; edge(int _t):t(_t){}};struct queryLca{ bool s; int t,n; queryLca(int _t,int _n,bool _s):t(_t),n(_n),s(_s){}};struct query{ int a,b,n; query(int _a,int _b,int _n):a(_a),b(_b),n(_n){}};struct info{ int Min,Max,Pro,RPro; info(int v=0):Min(v),Max(v),Pro(0),RPro(0){} info R() { info ans=*this; swap(ans.Pro,ans.RPro); return ans; } void Merge(const info& o) […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[10],"tags":[],"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/www.shuizilong.com\/wjmzbmr\/index.php?rest_route=\/wp\/v2\/posts\/120"}],"collection":[{"href":"https:\/\/www.shuizilong.com\/wjmzbmr\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.shuizilong.com\/wjmzbmr\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.shuizilong.com\/wjmzbmr\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.shuizilong.com\/wjmzbmr\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=120"}],"version-history":[{"count":0,"href":"https:\/\/www.shuizilong.com\/wjmzbmr\/index.php?rest_route=\/wp\/v2\/posts\/120\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.shuizilong.com\/wjmzbmr\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=120"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.shuizilong.com\/wjmzbmr\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=120"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.shuizilong.com\/wjmzbmr\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=120"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}