POJ 2763

题意：给一个数，边之间有权值，然后两种操作，第一种：求任意两点的权值和，第二，修改树上两点的权值。

 #pragma comment(linker, "/STACK:1024000000,1024000000")
 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <algorithm>
 using namespace std;
 #define N 100010
 #define ls o<<1
 #define rs o<<1|1
 #define define_m int m=(l+r)>>1
 #define ll long long

 int first[N] , k;

 struct Edge{
     int x , y , next , w;
     Edge(){}
     Edge(int x , int y , int next , int w):x(x),y(y),next(next),w(w){}
 }e[N<<];

 void add_edge(int x , int y , int w)
 {
     e[k] = Edge(x , y , first[x] , w);
     first[x] = k++;
 }

 int sz[N] , fa[N] , son[N] , dep[N] , id[N] , top[N] , num;

 void dfs(int u , int f , int d)
 {
     sz[u] =  , fa[u] = f , dep[u] = d , son[u]=;
     int maxn=;
     for(int i=first[u] ; ~i ; i=e[i].next){
         int v = e[i].y;
         if(v == f) continue;
         dfs(v , u , d+);
         sz[u] += sz[v];
         if(sz[v]>maxn) maxn=sz[v] , son[u]=v;
     }
 }

 void dfs1(int u , int f , int head)
 {
     top[u] = head;
     id[u] = ++num;
     if(son[u]){
         dfs1(son[u] , u , head);
     }
     for(int i=first[u] ; ~i ; i=e[i].next){
         int v = e[i].y;
         if(v == f || v == son[u]) continue;
         dfs1(v , u , v);
     }
 }

 int n , q , src , val[N] , sum[N<<];

 void push_up(int o)
 {
     sum[o] = sum[ls]+sum[rs];
 }

 void build(int o , int l , int r)
 {
     if(l==r){
         sum[o] = val[l];
         return;
     }
     define_m;
     build(ls , l , m);
     build(rs , m+ , r);
     push_up(o);
 }

 void update(int o , int l , int r , int p , int v)
 {
     if(l==r){
         sum[o] = v;
         return;
     }
     define_m;
     if(m>=p) update(ls , l , m , p , v);
     else update(rs , m+ , r , p , v);
     push_up(o);
 }

 int query(int o , int l , int r , int s , int t)
 {
     if(l>=s && r<=t) return sum[o];
     define_m;
     int ans = ;
     if(m>=s) ans+=query(ls , l , m , s , t);
     if(m<t) ans+=query(rs , m+ , r , s , t);
     return ans;
 }

 int calPath(int u , int v)
 {
     int top1 = top[u] , top2 = top[v];
     int ans = ;
     while(top1!=top2){
         if(dep[top1]<dep[top2]){
             swap(top1 , top2);
             swap(u , v);
         }
         ans += query( ,  , num , id[top1] , id[u]);
       //  cout<<"range: "<<id[top1]<<" "<<id[u]<<" "<<ans<<endl;
         u = fa[top1];
         top1 = top[u];
     }
     if(u!=v){
         if(dep[u]<dep[v]) swap(u , v);
         ans += query( ,  , num , id[son[v]] , id[u]);
     }
     return ans;
 }

 int main()
 {
    // freopen("in.txt" , "r" , stdin);
     while(~scanf("%d%d%d" , &n , &q , &src)){
         memset(first , - , sizeof(first));
         k = ;
         for(int i= ; i<n- ; i++){
             int u , v , w;
             scanf("%d%d%d" , &u , &v , &w);
             add_edge(u , v , w);
             add_edge(v , u , w);
         }
         num = ;
         dfs( ,  , );
         dfs1( ,  , );
       //  for(int i=1 ; i<=n ; i++) cout<<i<<" "<<son[i]<<" "<<id[i]<<endl;
         for(int i= ; i<n- ; i++){
             int j = i<<;
             if(fa[e[j].x] != e[j].y) val[id[e[j].y]] = e[j].w;
             else val[id[e[j].x]] = e[j].w;
         }
         build( ,  , num);
         int en , op , t;
         while(q--){
             scanf("%d" , &op);
             if(op){
                 scanf("%d%d" , &t , &en);
                 t--;
                 int pos;
                 if(fa[e[t*].x] != e[t*].y) pos = id[e[t*].y];
                 else pos = id[e[t*].x];
              //   cout<<"update: "<<pos<<endl;
                 update( ,  , num , pos , en);
             }
             else{
                 scanf("%d" , &en);
                 int ans = calPath(src , en);
                 printf("%d\n" ,ans);
                 src = en;
             }
         }
     }
     return ;
 }