FZU 2082 过路费

树链剖分模板题

 #include <cstdio>
 #include <iostream>
 #include <cstring>
 #include <algorithm>
 using namespace std;
 #define N 50010
 #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;
 }e[N<<];

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

 int sz[N] , dep[N] , fa[N] , son[N] , top[N] , id[N] , num;
 void dfs(int u , int f , int d)
 {
     fa[u] = f , sz[u] =  , dep[u]= d , son[u]=;
     int mx = ;
     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]>mx) mx=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);
     }
 }

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

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

 ll calPath(int u , int v)
 {
     int top1 = top[u] , top2 = top[v] ;
     ll ret=;
     while(top1!=top2){
         if(dep[top1]<dep[top2]){
             swap(top1 , top2);
             swap(u , v);
         }
         ret+=qSum( ,  , num , id[top1] , id[u]);
         u = fa[top1];
         top1 = top[u];
     }
     if(u!=v){
         if(dep[u]<dep[v]) swap(u,v);
         ret+=qSum(,,num,id[son[v]],id[u]);
     }
     return ret;
 }

 int main()
 {
   //  freopen("in.txt" , "r" , stdin);
     int n , m , x , y , w;
     while(scanf("%d%d" , &n , &m)!=EOF)
     {
         memset(first , - , sizeof(first));
         k = ;
         for(int i= ; i<n- ; i++){
             scanf("%d%d%d" , &x , &y , &w);
             add_edge(x , y , w);
             add_edge(y , x , w);
         }
         dfs( ,  , );
         num = ;
         dfs1( ,  , );
         for(int i= ; i<n- ; i++){
             x = e[i*].x , y = e[i*].y;
             if(fa[x]!=y) val[id[y]] = e[i*].w;
             else val[id[x]] = e[i*].w;
         }
         build( ,  , num);
         while(m--){
             scanf("%d%d%d" , &w , &x , &y);
             if(w){
                 printf("%I64d\n" , calPath(x , y));
             }else{
                 x--;
                 int pos;
                 if(fa[e[x*].x]!=e[x*].y) pos = id[e[x*].y];
                 else pos = id[e[x*].x];
                 update( ,  , num , pos , y);
             }
         }
     }
     return ;
 }