[bzoj] 1036 Count
原题
树链剖分板子题
树剖详解:
#include<cstdio>
#include<algorithm>
typedef long long ll;
#define N 30010
using namespace std;
int n,x,y,m,a[N],f[N],dfn[N],deep[N],head[N],cnt=1,tp[N],ref[N],t,son[N],size[N];
char s[10];
struct hhh
{
int to,next;
}edge[2*N];
struct node
{
int l,r,data,mx;
}tre[4*N];
int read()
{
int ans=0,fu=1;
char j=getchar();
for (;(j<'0' || j>'9') && j!='-';j=getchar()) ;
if (j=='-') fu=-1,j=getchar();
for (;j>='0' && j<='9';j=getchar()) ans*=10,ans+=j-'0';
return ans*fu;
}
void add(int u,int v)
{
edge[cnt].to=v;
edge[cnt].next=head[u];
head[u]=cnt++;
}
void dfs1(int x,int fa,int dep)
{
f[x]=fa;
deep[x]=dep+1;
int mx=0;
for (int i=head[x],v;i;i=edge[i].next)
{
v=edge[i].to;
if (v!=fa)
{
dfs1(v,x,dep+1);
size[x]+=size[v];
if (size[v]>mx) son[x]=v,mx=size[v];
}
}
size[x]++;
}
void dfs2(int x,int top)
{
dfn[x]=++t;
ref[t]=x;
tp[x]=top;
if (son[x]) dfs2(son[x],top);
for (int i=head[x],v;i;i=edge[i].next)
{
v=edge[i].to;
if (v!=son[x] && v!=f[x])
dfs2(v,v);
}
}
void build(int i,int l,int r)
{
tre[i].l=l;
tre[i].r=r;
if (l==r)
{
tre[i].data=a[ref[l]];
tre[i].mx=a[ref[l]];
return ;
}
int mid=(l+r)>>1;
build(i*2,l,mid);
build(i*2+1,mid+1,r);
tre[i].data=tre[i*2].data+tre[i*2+1].data;
tre[i].mx=max(tre[i*2].mx,tre[i*2+1].mx);
}
void modify(int i,int x,int y)
{
if (tre[i].l==x && tre[i].l==tre[i].r)
{
tre[i].data=y;
tre[i].mx=y;
return ;
}
int mid=(tre[i].l+tre[i].r)>>1;
if (x>mid) modify(i*2+1,x,y);
else modify(i*2,x,y);
tre[i].data=tre[i*2].data+tre[i*2+1].data;
tre[i].mx=max(tre[i*2].mx,tre[i*2+1].mx);
}
ll query(int i,int l,int r,int p)
{
if (tre[i].l==l && tre[i].r==r)
if (p) return tre[i].data;
else return tre[i].mx;
int mid=(tre[i].l+tre[i].r)>>1;
if (l>mid) return query(i*2+1,l,r,p);
else if (r<=mid) return query(i*2,l,r,p);
else if (p) return query(i*2,l,mid,p)+query(i*2+1,mid+1,r,p);
else return max(query(i*2,l,mid,p),query(i*2+1,mid+1,r,p));
}
ll pathquery(int u,int v,int p)
{
ll ans=0,tmp=-1000000000;
while (tp[u]!=tp[v])
{
if (deep[tp[u]]<deep[tp[v]]) swap(u,v);
if (p) ans+=query(1,dfn[tp[u]],dfn[u],p);
else tmp=max(tmp,query(1,dfn[tp[u]],dfn[u],p));
u=f[tp[u]];
}
if (deep[u]>deep[v]) swap(u,v);
if (p) return ans+query(1,dfn[u],dfn[v],p);
else return max(tmp,query(1,dfn[u],dfn[v],p));
}
int main()
{
n=read();
for (int i=1;i<n;i++)
{
x=read();
y=read();
add(x,y);
add(y,x);
}
for (int i=1;i<=n;i++) a[i]=read();
dfs1(1,0,0);
dfs2(1,1);
build(1,1,n);
m=read();
while (m--)
{
scanf("%s",s);
x=read();
y=read();
if (s[1]=='M')
printf("%lld\n",pathquery(x,y,0));
else if (s[1]=='S')
printf("%lld\n",pathquery(x,y,1));
else modify(1,dfn[x],y);
}
return 0;
}