spoj375

题解：

树链剖分的模板题

具体代码详见网上的其他代码

代码：

#include<cstdio>
#include<cmath>
#include<cstring>
#include<algorithm>
using namespace std;
const int N=;
char s[];
int data[N],p[N],n,pos,fp[N],num[N];
int x,y,z,tot,top[N],T,e[N][],val[N],deep[N],son[N],fa[N],ne[N],fi[N],zz[N];
void jb(int x,int y)
{
    ne[++tot]=fi[x];
    fi[x]=tot;
    zz[tot]=y;
}
void dfs1(int x,int y,int z)
{
    deep[x]=z;
    fa[x]=y;
    for (int i=fi[x];i;i=ne[i])
     {
         int k=zz[i];
         if (k!=y)
          {
              dfs1(k,x,z+);
              num[x]+=num[k];
              if (son[x]==-||(num[son[x]]<num[k]))son[x]=k;
          }
     }
}
void dfs2(int x,int y)
{
    top[x]=y;
    if (son[x]!=-)
     {
         p[x]=pos++;
         fp[p[x]]=x;
         dfs2(son[x],y);
     }
    else
     {
         p[x]=pos++;
         fp[p[x]]=x;
         return;
     }
    for (int i=fi[x];i;i=ne[i])
     if (zz[i]!=son[x]&&zz[i]!=fa[x])
      dfs2(zz[i],zz[i]);
}
void pushup(int x)
{
    data[x]=max(data[x*],data[x*+]);
}
void build(int l,int r,int x)
{
    if (l==r)
     {
         data[x]=val[l];
         return;
     }
    int mid=(l+r)/;
    build(l,mid,x*);
    build(mid+,r,x*+);
    pushup(x);
}
void updata(int p,int q,int l,int r,int x)
{
    if (l==r)
     {
         data[x]=q;
         return;
     }
    int mid=(l+r)/;
    if (p<=mid)updata(p,q,l,mid,x*);
    else updata(p,q,mid+,r,x*+);
    pushup(x);
}
int query(int x,int y,int l,int r,int s)
{
    if (x>r||y<l)return ;
    if (x<=l&&y>=r)return data[s];
    int mid=(l+r)/;
    return max(query(x,y,l,mid,s*),query(x,y,mid+,r,s*+));
}
int find(int x,int y)
{
    int f1=top[x],f2=top[y],temp=;
    while (f1!=f2)
     {
         if (deep[f1]<deep[f2])
          {
              swap(x,y);
              swap(f1,f2);
          }
         temp=max(temp,query(p[f1],p[x],,n,));
         x=fa[f1],f1=top[x];
     }
    if (x==y)return temp;
    if (deep[x]>deep[y])swap(x,y);
    return max(temp,query(p[son[x]],p[y],,n,));
}
int read()
{
    int x=;char c;
    for (;c<''||c>'';c=getchar());
    for (;c>=''&&c<='';c=getchar())x=x*+c-;
    return x;
}
int main()
{
    scanf("%d",&T);
    while (T--)
     {
         pos=;tot=;
         memset(fi,,sizeof fi);
         memset(son,-,sizeof son);
         memset(data,,sizeof data);
         scanf("%d",&n);
         for (int i=;i<n-;i++)
          {
              scanf("%d%d%d",&e[i][],&e[i][],&e[i][]);
              jb(e[i][],e[i][]);jb(e[i][],e[i][]);
          }
         dfs1(,,);
        dfs2(,);
        for (int i=;i<n-;i++)
         {
             if (deep[e[i][]]<deep[e[i][]])swap(e[i][],e[i][]);
             val[p[e[i][]]]=e[i][];
         }
        build(,n,);
         while (scanf("%s",&s))
          {
              if (s[]=='D')break;
              x=read();y=read();
              if (s[]=='Q')printf("%d\n",find(x,y));
              else updata(p[e[x-][]],y,,n,);
          }
     }
    return ;
}