【算法】树链剖分+线段树
【题解】模板题，见http://www.cnblogs.com/onioncyc/p/6207462.html
调用线段数时要用新编号pos[i] ！！！
#include<cstdio>
#include<cctype>
#include<algorithm>
using namespace std;
const int maxn=,inf=0x3f3f3f3f;
int pos[maxn],top[maxn],dfsnum,f[maxn],deep[maxn],size[maxn],first[maxn],n,tot,a[maxn];
struct edge{int u,v,from;}e[maxn*];
struct tree{int l,r,sum,mx;}t[maxn*];
int read()
{
char c;int s=,t=;
while(!isdigit(c=getchar()))if(c=='-')t=-;
do{s=s*+c-'';}while(isdigit(c=getchar()));
return s*t;
}
void insert(int u,int v)
{tot++;e[tot].u=u;e[tot].v=v;e[tot].from=first[u];first[u]=tot;}
void dfs1(int x,int fa)
{
size[x]=;
for(int i=first[x];i;i=e[i].from)
if(e[i].v!=fa)
{
int y=e[i].v;
deep[y]=deep[x]+;
f[y]=x;
dfs1(y,x);
size[x]+=size[y];
}
}
void dfs2(int x,int tp,int fa)
{
int k=;
pos[x]=++dfsnum;
top[x]=tp;
for(int i=first[x];i;i=e[i].from)
if(e[i].v!=fa&&size[e[i].v]>size[k])k=e[i].v;
if(k==)return;
dfs2(k,tp,x);
for(int i=first[x];i;i=e[i].from)
if(e[i].v!=fa&&e[i].v!=k)dfs2(e[i].v,e[i].v,x);
}
void build(int k,int l,int r)
{
t[k].l=l;t[k].r=r;
if(l!=r)
{
int mid=(l+r)>>;
build(k<<,l,mid);
build(k<<|,mid+,r);
}
}
void change(int k,int x,int y)
{
int left=t[k].l,right=t[k].r;
if(left==right){t[k].mx=y;t[k].sum=y;}
else
{
int mid=(left+right)>>;
if(x<=mid)change(k<<,x,y);
else change(k<<|,x,y);
t[k].sum=t[k<<].sum+t[k<<|].sum;
t[k].mx=max(t[k<<].mx,t[k<<|].mx);
}
}
int ask_mx(int k,int l,int r)
{
int left=t[k].l,right=t[k].r;
if(l<=left&&right<=r)return t[k].mx;
else
{
int mid=(left+right)>>,maxs=-inf;
if(l<=mid)maxs=ask_mx(k<<,l,r);
if(r>mid)maxs=max(maxs,ask_mx(k<<|,l,r));
return maxs;
}
}
int ask_sum(int k,int l,int r)
{
int left=t[k].l,right=t[k].r;
if(l<=left&&right<=r)return t[k].sum;
else
{
int mid=(left+right)>>,sums=;
if(l<=mid)sums=ask_sum(k<<,l,r);
if(r>mid)sums+=ask_sum(k<<|,l,r);
return sums;
}
}
int solve_mx(int x,int y)
{
int maxs=-inf;
while(top[x]!=top[y])
{
if(deep[top[x]]<deep[top[y]])swap(x,y);
maxs=max(maxs,ask_mx(,pos[top[x]],pos[x]));
x=f[top[x]];
}
if(pos[x]>pos[y])swap(x,y);
maxs=max(maxs,ask_mx(,pos[x],pos[y]));
return maxs;
}
int solve_sum(int x,int y)
{
int sums=;
while(top[x]!=top[y])
{
if(deep[top[x]]<deep[top[y]])swap(x,y);
sums+=ask_sum(,pos[top[x]],pos[x]);
x=f[top[x]];
}
if(pos[x]>pos[y])swap(x,y);
sums+=ask_sum(,pos[x],pos[y]);
return sums;
}
int main()
{
n=read();
for(int i=;i<n;i++)
{
int u=read(),v=read();
insert(u,v);
insert(v,u);
}
for(int i=;i<=n;i++)a[i]=read();
dfs1(,-);
dfs2(,,-);
build(,,n);
for(int i=;i<=n;i++)change(,pos[i],a[i]);
int Q=read();char ch[];
for(int i=;i<=Q;i++)
{
scanf("%s",ch);
int u=read(),v=read();
if(ch[]=='H')change(,pos[u],v);//QAQ 调用线段树必须用新编号，下面用旧编号是因为子程序中用了新编号T_T
if(ch[]=='M')printf("%d\n",solve_mx(u,v));
if(ch[]=='S')printf("%d\n",solve_sum(u,v));
}
return ;
}