题意:
维护树上区间最值和区间和,加上单点修改
题解:
树链剖分的题,我们只要把线段树部分的操作写好,这题也就那回事,毕竟树链剖分是个模板,而且好理解,注意不要用
cin和cout
会 TLE
AC代码:
#include<bits/stdc++.h>
using namespace std;
#define ll long long
const ll maxn=3e5+5;
ll cnt,cnx,head[maxn];
ll top[maxn],son[maxn],deep[maxn],a[maxn];
ll sizx[maxn],dfn[maxn],pre[maxn],w[maxn];
struct node
{
ll to,nex;
} edge[maxn<<1];
void add(ll u,ll v)
{
edge[cnx].to=v;
edge[cnx].nex=head[u];
head[u]=cnx++;
}
void dfs1(ll u,ll fa)
{
deep[u]=deep[fa]+1;
pre[u]=fa;
sizx[u]=1;
ll maxson=-1;
for(ll i=head[u]; ~i; i=edge[i].nex)
{
ll v=edge[i].to;
if(v!=fa)
{
dfs1(v,u);
sizx[u]+=sizx[v];
if(sizx[v]>maxson)
{
maxson=sizx[v];
son[u]=v;
}
}
}
}
void dfs2(ll u,ll t)
{
top[u]=t;
dfn[u]=++cnt;
w[cnt]=a[u];
if(!son[u])
{
return ;
}
dfs2(son[u],t);
for(ll i=head[u]; ~i; i=edge[i].nex)
{
ll v=edge[i].to;
if(v==pre[u]||v==son[u])
continue;
dfs2(v,v);
}
}
struct yzj
{
ll l,r,sum,ma;
} tr[maxn<<2];
void pushup(ll k)
{
tr[k].sum=tr[k<<1].sum+tr[k<<1|1].sum;
tr[k].ma=max(tr[k<<1].ma,tr[k<<1|1].ma);
}
void build(ll k,ll l,ll r)
{
tr[k].l=l,tr[k].r=r;
if(l==r)
{
tr[k].sum=w[l];
tr[k].ma=w[l];
return ;
}
ll mid=l+r>>1;
build(k<<1,l,mid);
build(k<<1|1,mid+1,r);
pushup(k);
}
void modify(ll k,ll pos,ll w)
{
if(tr[k].l==tr[k].r)
{
tr[k].ma=w;
tr[k].sum=w;
return ;
}
ll mid=tr[k].l+tr[k].r>>1;
if(mid>=pos)
{
modify(k<<1,pos,w);
}
else
{
modify(k<<1|1,pos,w);
}
pushup(k);
}
ll askm(ll k,ll l,ll r)
{
if(tr[k].l>=l&&tr[k].r<=r)
{
return tr[k].ma;
}
ll mid=tr[k].l+tr[k].r>>1;
if(mid>=r)
{
return askm(k<<1,l,r);
}
else if(mid<l)
{
return askm(k<<1|1,l,r);
}
else
{
return max(askm(k<<1,l,mid),askm(k<<1|1,mid+1,r));
}
}
ll asks(ll k,ll l,ll r)
{
if(tr[k].l>=l&&tr[k].r<=r)
{
return tr[k].sum;
}
ll mid=tr[k].l+tr[k].r>>1;
if(mid>=r)
{
return asks(k<<1,l,r);
}
else if(mid<l)
{
return asks(k<<1|1,l,r);
}
else
{
return (asks(k<<1,l,mid)+asks(k<<1|1,mid+1,r));
}
}
ll optm(ll x,ll y)
{
ll res=~0x3f3f3f3f;
while(top[x]!=top[y])
{
if(deep[top[x]]<deep[top[y]])
swap(x,y);
res=max(res,askm(1,dfn[top[x]],dfn[x]));
x=pre[top[x]];
}
if(deep[x]>deep[y])
{
swap(x,y);
}
res=max(res,askm(1,dfn[x],dfn[y]));
return res;
}
ll opts(ll x,ll y)
{
ll res=0;
while(top[x]!=top[y])
{
if(deep[top[x]]<deep[top[y]])
swap(x,y);
res+=asks(1,dfn[top[x]],dfn[x]);
x=pre[top[x]];
}
if(deep[x]>deep[y])
{
swap(x,y);
}
res+=asks(1,dfn[x],dfn[y]);
return res;
}
int main()
{
ll n,u,v;
memset(head,-1,sizeof(head));
scanf("%lld",&n);
for(ll i=1; i<n; i++)
{
scanf("%lld %lld",&u,&v);
add(u,v);
add(v,u);
}
for(ll i=1; i<=n; i++)
scanf("%lld",&a[i]);
dfs1(1,0);
dfs2(1,1);
build(1,1,n);
ll q;
scanf("%lld",&q);
char s[10];
while(q--)
{
ll x,y;
scanf("%s %lld %lld",s,&x,&y);
if(strcmp(s,"QMAX")==0)
{
printf("%lld\n",optm(x,y));
}
else if(strcmp(s,"QSUM")==0)
{
printf("%lld\n",opts(x,y));
}
else
{
modify(1,dfn[x],y);
}
}
}