树链剖分

void dfs1(int u,int fa,int depth){    dep[u]=depth;    f[u]=fa;sz[u]=1;son[u]=-1;    for(int i=first[u];i!=-1;i=edge[i].next)    {        int v=edge[i].e;        if(v==fa) continue;        dfs1(v,u,depth+1);        up[v]=edge[i].w;        sz[u]+=sz[v];        if(son[u]==-1||sz[son[u]]<sz[v]) son[u]=v;    }}void dfs2(int u,int tp){    top[u]=tp;    id[u]=++mark;    p[mark]=u;    if(son[u]==-1) return;    dfs2(son[u],tp);    for(int i=first[u];i!=-1;i=edge[i].next)    {        int v=edge[i].e;        if(v==f[u]||v=son[u]) continue;        dfs2(v,v);    }}void change(int u,int v,int w){    int tu=top[u];    int tv=top[v];    while(tu!=tv)    {        if(dep[tu]<dep[tv])        {            swap(tu,tv);            swap(u,v);        }        update(id[tu],id[u],1,n,1,w);        u=f[tu];        tu=top[u];    }    if(u==v) return;//根据是边权还是点权修改    if(dep[u]<dep[v]) swap(u,v);    update(id[son[v]],id[u],1,n,1,w);}