FZU 2082 过路费 (树链剖分 修改单边权)

题目链接：http://acm.fzu.edu.cn/problem.php?pid=2082

树链剖分模版题，求和，修改单边权。

 #include <iostream>
 #include <cstdio>
 #include <algorithm>
 #include <cstring>
 using namespace std;
 typedef long long LL;
 const int MAXN = 5e4 + ;
 struct EDGE {
     int to , next;
     LL cost;
 }edge[MAXN << ];
 int from[MAXN] , to[MAXN] , head[MAXN] , cnt , tot;
 LL cost[MAXN] , val[MAXN] , dis[MAXN];
 int top[MAXN] , dep[MAXN] , size[MAXN] , son[MAXN] , par[MAXN] , id[MAXN];

 void init() {
     memset(head , - , sizeof(head));
     cnt = tot = ;
 }

 inline void add(int u , int v , LL cost) {
     edge[tot].next = head[u];
     edge[tot].to = v;
     edge[tot].cost = cost;
     head[u] = tot++;
 }

 void dfs1(int u , int p , int d) {
     dep[u] = d , par[u] = p , size[u] =  , son[u] = u;
     for(int i = head[u] ; ~i ; i = edge[i].next) {
         int v = edge[i].to;
         if(v == p)
             continue;
         dfs1(v , u , d + );
         if(size[v] > size[son[u]])
             son[u] = v;
         size[u] += size[v];
     }
 }

 void dfs2(int u , int p , int t) {
     top[u] = t , id[u] = ++cnt;
     if(son[u] != u)
         dfs2(son[u] , u , t);
     for(int i = head[u] ; ~i ; i = edge[i].next) {
         int v = edge[i].to;
         if(v == son[u] || v == p)
             continue;
         dfs2(v , u , v);
     }
 }

 struct SegTree {
     int l , r;
     LL sum;
 }T[MAXN << ];

 void build(int p , int l , int r) {
     int mid = (l + r) >> ;
     T[p].l = l , T[p].r = r;
     if(l == r) {
         T[p].sum = val[l];
         return ;
     }
     build(p <<  , l , mid);
     build((p << )| , mid +  , r);
     T[p].sum = T[p << ].sum + T[(p << )|].sum;
 }

 void updata(int p , int pos , LL num) {
     int mid = (T[p].l + T[p].r) >> ;
     if(T[p].l == T[p].r && T[p].l == pos) {
         T[p].sum = num;
         return ;
     }
     if(pos <= mid) {
         updata(p <<  , pos , num);
     }
     else {
         updata((p << )| , pos , num);
     }
     T[p].sum = T[p << ].sum + T[(p << )|].sum;
 }

 LL query(int p , int l , int r) {
     int mid = (T[p].l + T[p].r) >> ;
     if(T[p].l == l && T[p].r == r) {
         return T[p].sum;
     }
     if(r <= mid) {
         return query(p <<  , l , r);
     }
     else if(l > mid) {
         return query((p << )| , l , r);
     }
     else {
         return query(p <<  , l , mid) + query((p << )| , mid +  , r);
     }
 }

 LL Find(int u , int v) {
     int fu = top[u] , fv = top[v];
     LL res = ;
     while(fu != fv) {
         if(dep[fu] >= dep[fv]) {
             res += query( , id[fu] , id[u]);
             u = par[fu];
             fu = top[u];
         }
         else {
             res += query( , id[fv] , id[v]);
             v = par[fv];
             fv = top[v];
         }
     }
     if(v == u)
         return res;
     else if(dep[u] > dep[v])
         return res + query( , id[son[v]] , id[u]);
     else
         return res + query( , id[son[u]] , id[v]);
 }

 int main()
 {
     int n, m , l , r , c;
     while(~scanf("%d %d" , &n , &m)) {
         init();
         for(int i =  ; i < n ; ++i) {
             scanf("%d %d %lld" , from + i , to + i , cost + i);
             add(from[i] , to[i] , cost[i]);
             add(to[i] , from[i] , cost[i]);
         }
         dfs1( ,  , );
         dfs2( ,  , );
         //build(1 , 1 , cnt);
         for(int i =  ; i < n ; ++i) {
             if(dep[from[i]] < dep[to[i]])
                 swap(from[i] , to[i]);
             val[id[from[i]]] = cost[i];
             //updata(1 , id[from[i]] , cost[i]);
         }
         build( ,  , cnt);
         while(m--) {
             scanf("%d %d %d" , &c , &l , &r);
             if(c == ) {
                 updata( , id[from[l]] , (LL)r);
             }
             else {
                 printf("%d\n" , Find(l , r));
             }
         }
     }
 }