BZOJ 1036 [ZJOI2008]树的统计Count

#include<cstdio>
#include<algorithm>
#define MAXN 30010
using namespace std;
struct edge{int next,to;}e[MAXN*2];
struct segment{int sum, maxx, l, r;}node[MAXN*10];
const int INF = 1000000000;
int cnt=0;
int last[MAXN], siz[MAXN], son[MAXN], top[MAXN], fa[MAXN], dep[MAXN], w[MAXN];
int tree[MAXN], pre[MAXN], tcnt=0;
void add(int a,int b){e[++cnt]=(edge){last[a],b};last[a]=cnt;}
void build(int x, int l, int r)
{
node[x].l=l;
node[x].r=r;
if(l==r)
{
node[x].sum=node[x].maxx=w[pre[l]];
return;
}
int mid=(l+r)>>1;
build(x<<1,l,mid);
build(x<<1|1,mid+1,r);
node[x].sum=node[x<<1].sum+node[x<<1|1].sum;
node[x].maxx=max(node[x<<1].maxx,node[x<<1|1].maxx);
}
int ask_sum(int x, int l, int r)
{
if(r<node[x].l||node[x].r<l)
return 0;
if(l<=node[x].l&&node[x].r<=r)
return node[x].sum;
int mid=(node[x].l+node[x].r)>>1;
int ret=0;
if(l<=mid)ret+=ask_sum(x<<1,l,r);
if(mid+1<=r)ret+=ask_sum(x<<1|1,l,r);
return ret;
}
int ask_max(int x, int l, int r)
{
if(r<node[x].l||node[x].r<l)
return -INF;
if(l<=node[x].l&&node[x].r<=r)
return node[x].maxx;
int mid=(node[x].l+node[x].r)>>1;
int ret=-INF;
if(mid>=l)ret=max(ret,ask_max(x<<1,l,r));
if(mid+1<=r)ret=max(ret,ask_max(x<<1|1,l,r));
return ret;
}
void dfs1(int x)
{
dep[x]=dep[fa[x]]+1;
siz[x]=1;
for(int i = last[x]; i; i=e[i].next)
{
int y=e[i].to;
if(fa[x]!=y)
{
fa[y]=x;
dfs1(y);
siz[x]+=siz[y];
if(siz[y]>siz[son[x]])
son[x]=y;
}
}
}
void dfs2(int x)
{
if(son[fa[x]]==x)
top[x]=top[fa[x]];
else top[x]=x;
tree[x]=++tcnt;
pre[tcnt]=x;
if(son[x])dfs2(son[x]);
for(int i = last[x]; i; i=e[i].next)
if(e[i].to!=fa[x] && e[i].to!=son[x])
dfs2(e[i].to);
}
int qmax(int a, int b)
{
int ret=-INF;
while(top[a]!=top[b])
{
if(dep[top[a]]<dep[top[b]])
swap(a,b);
ret=max(ret,ask_max(1,tree[top[a]],tree[a]));
a=fa[top[a]];
}
if(dep[b]>dep[a])swap(a,b);
return max(ret,ask_max(1,tree[b],tree[a]));
}
int qsum(int a, int b)
{
int ret=0;
while(top[a]!=top[b])
{
if(dep[top[a]]<dep[top[b]])
swap(a,b);
ret+=ask_sum(1,tree[top[a]],tree[a]);
a=fa[top[a]];
}
if(dep[b]>dep[a])swap(a,b);
return ret+ask_sum(1,tree[b],tree[a]);
}
void update(int x, int p)
{
if(node[x].l==node[x].r)
{
node[x].sum=node[x].maxx=w[pre[node[x].l]];
return;
}
int mid=(node[x].l+node[x].r)>>1;
if(p<=mid)update(x<<1,p);
else update(x<<1|1,p);
node[x].sum=node[x<<1].sum+node[x<<1|1].sum;
node[x].maxx=max(node[x<<1].maxx,node[x<<1|1].maxx);
}
void change(int a, int b)
{
w[a]=b;
update(1,tree[a]);
}
int main()
{
int n;
scanf("%d",&n);
for(int i = 1; i < n; i++)
{
int a, b;
scanf("%d%d",&a,&b);
add(a,b);
add(b,a);
}
for(int i = 1; i <= n; i++)
scanf("%d",&w[i]);
dfs1(1);
dfs2(1);
build(1,1,n);
int q;
scanf("%d",&q);
for(;q--;)
{
char s[10];
int a, b;
scanf("%s%d%d",s,&a,&b);
if(s[1]=='M')
printf("%d\n",qmax(a,b));
else if(s[1]=='S')
printf("%d\n",qsum(a,b));
else
change(a,b);
}
return 0;
}