HDU_2586_How far away ？

How far away ？

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 18191    Accepted Submission(s): 7072

Problem Description

There are n houses in the village and some bidirectional roads connecting them. Every day peole always like to ask like this "How far is it if I want to go from house A to house B"? Usually it hard to answer. But luckily int this village the answer is always unique, since the roads are built in the way that there is a unique simple path("simple" means you can't visit a place twice) between every two houses. Yout task is to answer all these curious people.

 

Input

First line is a single integer T(T<=10), indicating the number of test cases.
  For each test case,in the first line there are two numbers n(2<=n<=40000) and m (1<=m<=200),the number of houses and the number of queries. The following n-1 lines each consisting three numbers i,j,k, separated bu a single space, meaning that there is a road connecting house i and house j,with length k(0<k<=40000).The houses are labeled from 1 to n.
  Next m lines each has distinct integers i and j, you areato answer the distance between house i and house j.

 

Output

For each test case,output m lines. Each line represents the answer of the query. Output a bland line after each test case.

 

Sample Input

2
3 2
1 2 10
3 1 15
1 2
2 3

2 2
1 2 100
1 2
2 1

 

Sample Output

10
25
100
100

 

Source

ECJTU 2009 Spring Contest

 

• LCA模板题
• 这里两种代码，一种离线tarjan一种在线RMQ+ST

 #include <iostream>
 #include <string>
 #include <cstdio>
 #include <cstring>
 #include <algorithm>
 #include <climits>
 #include <cmath>
 #include <vector>
 #include <queue>
 #include <stack>
 #include <set>
 #include <map>
 using namespace std;
 typedef long long           LL ;
 typedef unsigned long long ULL ;
 const int    maxn = 1e5 +    ;
 const int    inf  = 0x3f3f3f3f ;
 const int    npos = -         ;
 const int    mod  = 1e9 +     ;
 const int    mxx  =  +     ;
 const double eps  = 1e-       ;
 const double PI   = acos(-1.0) ;

 /* LCA + ST + RMQ Online */
 struct node{
     int v, next;
     LL w;
 };
 node edge[maxn<<];
 int fac[];
 int vis[maxn];
 int head[maxn<<], cnt;
 int ver[maxn<<], dep[maxn<<], first[maxn], tot;
 int dp[maxn<<][];
 LL dis[maxn];
 void addedge(int x, int y, LL z){
     edge[cnt].v=y;
     edge[cnt].w=z;
     edge[cnt].next=head[x];
     head[x]=cnt++;
 }
 void dfs(int u, int d){
     tot++;
     vis[u]=;
     ver[tot]=u;
     dep[tot]=d;
     first[u]=tot;
     for(int i=head[u];i!=-;i=edge[i].next){
         int v=edge[i].v;
         LL w=edge[i].w;
         if(!vis[v]){
             dis[v]=dis[u]+w;
             dfs(v,d+);
             tot++;
             ver[tot]=u;
             dep[tot]=d;
         }
     }
 }
 void ST(int n){
     int k=(int)(log((double)n)/log(2.0));
     for(int i=;i<=n;i++)
         dp[i][]=i;
     for(int j=;j<=k;j++)
         for(int i=;i+fac[j]-<=n;i++){
             int pl=dp[i][j-];
             int pr=dp[i+fac[j-]][j-];
             if(dep[pl]<dep[pr])
                 dp[i][j]=pl;
             else
                 dp[i][j]=pr;
         }
 }
 int RMQ(int l, int r){
     int k=(int)(log((double)(r-l+))/log(2.0));
     int pl=dp[l][k];
     int pr=dp[r-fac[k]+][k];
     if(dep[pl]<dep[pr])
         return pl;
     else
         return pr;
 }
 int LCA(int u, int v){
     int x=first[u];
     int y=first[v];
     if(x>y)swap(x,y);
     return ver[RMQ(x,y)];
 }
 int T, n, m, u, v;
 LL w;
 int main(){
     // freopen("in.txt","r",stdin);
     // freopen("out.txt","w",stdout);
     for(int i=;i<;i++)
         fac[i]=(<<i);
     while(~scanf("%d",&T)){
         while(T--){
             scanf("%d %d",&n,&m);
             cnt=;
             memset(head,-,sizeof(head));
             memset(vis,,sizeof(vis));
             for(int i=;i<n;i++){
                 scanf("%d %d %lld",&u,&v,&w);
                 addedge(u,v,w);
                 addedge(v,u,w);
             }
             dis[]=;
             tot=;
             dfs(,);
             ST(tot);
             while(m--){
                 scanf("%d %d",&u,&v);
                 printf("%lld\n",dis[u]+dis[v]-*dis[LCA(u,v)]);
             }
         }
     }
     return ;
 }

 #include <iostream>
 #include <string>
 #include <cstdio>
 #include <cstring>
 #include <algorithm>
 #include <climits>
 #include <cmath>
 #include <vector>
 #include <queue>
 #include <stack>
 #include <set>
 #include <map>
 using namespace std;
 typedef long long           LL ;
 typedef unsigned long long ULL ;
 const int    maxn = 1e5 +    ;
 const int    inf  = 0x3f3f3f3f ;
 const int    npos = -         ;
 const int    mod  = 1e9 +     ;
 const int    mxx  =  +     ;
 const double eps  = 1e-       ;
 const double PI   = acos(-1.0) ;

 /* Tarjan Offline */
 struct node{
     int v, next;
     LL w;
 };
 node edge[maxn<<], ask[maxn<<];
 int head0[maxn<<], cnt0;
 int head1[maxn<<], cnt1;
 int vis[maxn], fa[maxn];
 LL ans[], dis[maxn];
 void addedge(int x, int y, LL z, int flag){
     if(flag){
         ask[cnt1].v=y;
         ask[cnt1].w=z;
         ask[cnt1].next=head1[x];
         head1[x]=cnt1++;
     }else{
         edge[cnt0].v=y;
         edge[cnt0].w=z;
         edge[cnt0].next=head0[x];
         head0[x]=cnt0++;
     }
 }
 int find(int u){
     if(u==fa[u])
         return u;
     else
         return fa[u]=find(fa[u]);
     // return u==fa[u]?u:find(fa[u]);
 }
 void Union(int x, int y){
     int fx=find(x);
     int fy=find(y);
     if(fx!=fy)
         fa[fy]=fx;
 }
 void Tarjan(int u){
     vis[u]=;
     fa[u]=u;
     for(int i=head1[u];i!=-;i=ask[i].next){
         int v=ask[i].v;
         if(vis[v]){
             int lca=find(v);
             int id=ask[i].w;
             ans[id]=dis[u]+dis[v]-*dis[lca];
         }
     }
     for(int i=head0[u];i!=-;i=edge[i].next){
         int v=edge[i].v;
         LL w=edge[i].w;
         if(!vis[v]){
             dis[v]=dis[u]+w;
             Tarjan(v);
             Union(u,v);
         }
     }
 }
 int T, n, m, u, v;
 LL w;
 int main(){
     // freopen("in.txt","r",stdin);
     // freopen("out.txt","w",stdout);
     while(~scanf("%d",&T)){
         while(T--){
             scanf("%d %d",&n,&m);
             cnt0=;
             cnt1=;
             memset(head0,-,sizeof(head0));
             memset(head1,-,sizeof(head1));
             memset(vis,,sizeof(vis));
             for(int i=;i<n;i++){
                 scanf("%d %d %lld",&u,&v,&w);
                 addedge(u,v,w,);
                 addedge(v,u,w,);
             }
             for(int i=;i<=m;i++){
                 scanf("%d %d",&u,&v);
                 addedge(u,v,(LL)i,);
                 addedge(v,u,(LL)i,);
             }
             dis[]=;
             Tarjan();
             for(int i=;i<=m;i++)
                 printf("%lld\n",ans[i]);
         }
     }
     return ;
 }