洛谷$P$3066 逃跑的$BarnRunning\ Away\ From…$ $[USACO12DEC]$ 主席树

正解:主席树

解题报告:

传送门!

1551做$dp$实在是做不下去了,,,于是来水点儿别的题$QAQ$

然后这题,挺纸老虎的我$jio$得,,,看起来很难的样子然后仔细想下之后发现依然是个板子呢,,,$QwQ$

首先显然先树剖昂$QwQ$,然后子树内这个条件就变成了在某给定区间$[l,r]$内嘛

然后考虑这个所谓,距离$\leq x$怎么处理呢,不难想到先预处理出每个点距离根节点的$dis$,然后就变成了,求在$(dis_{u},dis_{u}+x]$这个范围内的数字有多少

欧克然后就成功板子掉辣$QwQ$

记得离散化,,,我之前没注意到$dis$和$l$的范围疯狂$MLE$调了半个小时才发现这个问题,,,被自己蠢到了$kk$

#include<bits/stdc++.h>
using namespace std;
#define il inline
#define gc getchar()
#define int long long
#define t(i) edge[i].to
#define w(i) edge[i].wei
#define ri register int
#define rb register bool
#define rc register char
#define rp(i,x,y) for(ri i=x;i<=y;++i)
#define my(i,x,y) for(ri i=x;i>=y;--i)
#define lb(x) lower_bound(st+1,st+sum+1,x)-st
#define ub(x) upper_bound(st+1,st+sum+1,x)-st
#define e(i,x) for(ri i=head[x];i;i=edge[i].nxt)

const int N=+,inf=1e18+;
int n,l,head[N],ed_cnt,dfn[N],low[N],rk[N],dfn_cnt,sum,dis[N],rt[N],nod_cnt,st[N];
struct ed{int to,nxt,wei;}edge[N];
struct node{int l,r,num;}tr[N<<];

il int read()
{
    rc ch=gc;ri x=;rb y=;
    while(ch!='-' && (ch>'' || ch<''))ch=gc;
    if(ch=='-')ch=gc,y=;
    while(ch>='' && ch<='')x=(x<<)+(x<<)+(ch^''),ch=gc;
    return y?x:-x;
}
il void ad(ri x,ri y,ri z){edge[++ed_cnt]=(ed){x,head[y],z};head[y]=ed_cnt;}
void dfs(ri x)
{
    rk[dfn[x]=low[x]=++dfn_cnt]=x;
    e(i,x)st[++sum]=dis[t(i)]=dis[x]+w(i),dfs(t(i)),low[x]=low[t(i)];
}
int modify(ri d,ri l,ri r,ri dat)
{
    ri nw=++nod_cnt;tr[nw]=tr[d];if(l==r)return ++tr[nw].num,nw;
    ri mid=(l+r)>>;mid>=dat?tr[nw].l=modify(tr[d].l,l,mid,dat):tr[nw].r=modify(tr[d].r,mid+,r,dat);
    tr[nw].num=tr[tr[nw].l].num+tr[tr[nw].r].num;return nw;
}
int query(ri rt_l,ri rt_r,ri l,ri r,ri to_l,ri to_r)
{
    if(to_l<=l && r<=to_r)return tr[rt_r].num-tr[rt_l].num;
    ri mid=(l+r)>>,ret=;
    if(mid>=to_l)ret+=query(tr[rt_l].l,tr[rt_r].l,l,mid,to_l,to_r);
    if(mid<to_r)ret+=query(tr[rt_l].r,tr[rt_r].r,mid+,r,to_l,to_r);
    return ret;
}

signed main()
{
    //freopen("3066.in","r",stdin);freopen("3066.out","w",stdout);
    n=read();l=read();rp(i,,n){ri x=read(),len=read();ad(i,x,len);}
    dfs();st[++sum]=inf;st[++sum]=;sort(st+,st++sum);sum=unique(st+,st++sum)-st-;
    rp(i,,n)rt[i]=modify(rt[i-],,sum,lb(dis[rk[i]]));
    rp(i,,n)printf("%lld\n",query(rt[dfn[i]-],rt[low[i]],,sum,lb(dis[i]),lb(dis[i]+l+)-));
    return ;
}