FZU 2082 过路费 (树链剖分)

树链剖分裸题。。。不多说。。
代码如下：

#include <iostream>
#include <string.h>
#include <math.h>
#include <queue>
#include <algorithm>
#include <stdlib.h>
#include <map>
#include <set>
#include <stdio.h>
using namespace std;
#define LL long long
#define pi acos(-1.0)
//#pragma comment(linker, "/STACK:1024000000")
const int mod=1e9+7;
const int INF=0x3f3f3f3f;
const double eqs=1e-3;
const int MAXN=50000+10;
#define root 1, tot, 1
#define lson l, mid, rt<<1
#define rson mid+1, r, rt<<1|1
int head[MAXN], cnt, tot;
int siz[MAXN], top[MAXN], fa[MAXN], w[MAXN], son[MAXN], dep[MAXN];
int sum[MAXN<<2];
struct node
{
        int u, v, w, next;
}edge[MAXN<<1];
void add(int u,int v, int w)
{
        edge[cnt].u=u;
        edge[cnt].v=v;
        edge[cnt].w=w;
        edge[cnt].next=head[u];
        head[u]=cnt++;
}
void init()
{
        memset(head,-1,sizeof(head));
        cnt=tot=0;
        memset(dep,0,sizeof(dep));
        memset(son,0,sizeof(son));
        memset(sum,0,sizeof(sum));
}
void dfs1(int u, int p)
{
        siz[u]=1;
        for(int i=head[u];i!=-1;i=edge[i].next){
                int v=edge[i].v;
                if(v==p) continue ;
                fa[v]=u;
                dep[v]=dep[u]+1;
                dfs1(v,u);
                siz[u]+=siz[v];
                if(siz[son[u]]<siz[v])son[u]=v;
        }
}
void dfs2(int u, int tp)
{
        w[u]=++tot;top[u]=tp;
        if(son[u]) dfs2(son[u],tp);
        for(int i=head[u];i!=-1;i=edge[i].next){
                int v=edge[i].v;
                if(v!=fa[u]&&v!=son[u])
                        dfs2(v,v);
        }
}
struct Line_Tree
{
        void PushUp(int rt)
        {
                sum[rt]=sum[rt<<1]+sum[rt<<1|1];
        }
        void Update(int p, int x, int l, int r, int rt)
        {
                if(l==r){
                        sum[rt]=x;
                        return ;
                }
                int mid=l+r>>1;
                if(p<=mid) Update(p,x,lson);
                else Update(p,x,rson);
                PushUp(rt);
        }
        int Query(int ll, int rr, int l, int r, int rt)
        {
                if(ll<=l&&rr>=r){
                        return sum[rt];
                }
                int mid=l+r>>1, ans=0;
                if(ll<=mid) ans+=Query(ll,rr,lson);
                if(rr>mid) ans+=Query(ll,rr,rson);
                return ans;
        }
}lt;
int solve(int u, int v)
{
        int f1=top[u], f2=top[v], ans=0;
        while(f1!=f2){
                if(dep[f1]<dep[f2]){
                        swap(u,v);
                        swap(f1,f2);
                }
                ans+=lt.Query(w[f1],w[u],root);
                u=fa[f1];f1=top[u];
        }
        if(u==v) return ans;
        if(dep[u]<dep[v]) swap(u,v);
        return ans+lt.Query(w[son[v]],w[u],root);
}
int main()
{
        int n, m, i, j, x, u, v, c, id;
        while(scanf("%d%d",&n,&m)!=EOF){
                init();
                for(i=1;i<n;i++){
                        scanf("%d%d%d",&u,&v,&c);
                        add(u,v,c);
                        add(v,u,c);
                }
                dfs1(1,-1);
                dfs2(1,1);
                for(i=0;i<cnt;i+=2){
                        u=edge[i].u;
                        v=edge[i].v;
                        if(dep[u]<dep[v]) swap(u,v);
                        lt.Update(w[u],edge[i].w,root);
                }
                while(m--){
                        scanf("%d",&x);
                        if(x){
                                scanf("%d%d",&u,&v);
                                printf("%d\n",solve(u,v));
                        }
                        else{
                                scanf("%d%d",&id,&c);
                                u=edge[id-1<<1].u;
                                v=edge[id-1<<1].v;
                                if(dep[u]<dep[v]) swap(u,v);
                                lt.Update(w[u],c,root);
                        }
                }
        }
        return 0;
}