洛谷P3642 [APIO2016]烟火表演

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题解

fy大佬好强……我根本看不懂……

//minamoto
#include<bits/stdc++.h>
#define ll long long
using namespace std;
#define getc() (p1==p2&&(p2=(p1=buf)+fread(buf,1,1<<21,stdin),p1==p2)?EOF:*p1++)
char buf[1<<21],*p1=buf,*p2=buf;
inline int read(){
    #define num ch-'0'
    char ch;bool flag=0;int res;
    while(!isdigit(ch=getc()))
    (ch=='-')&&(flag=true);
    for(res=num;isdigit(ch=getc());res=res*10+num);
    (flag)&&(res=-res);
    #undef num
    return res;
}
const int N=6e5+5;
int n,m,tot,fa[N],w[N],d[N],rt[N],L[N],R[N],dis[N];ll v[N],sum;
int merge(int x,int y){
    if(!x||!y) return x+y;
    if(v[x]<v[y]) swap(x,y);
    R[x]=merge(R[x],y);
    if(dis[L[x]]<dis[R[x]]) swap(L[x],R[x]);
    dis[x]=dis[R[x]]+1;return x;
}
int pop(int x){return merge(L[x],R[x]);}
int main(){
//    freopen("testdata.in","r",stdin);
    n=read(),m=read();
    for(int i=2;i<=n+m;++i)
    fa[i]=read(),w[i]=read(),sum+=w[i],++d[fa[i]];
    for(int i=n+m;i>=2;--i){
        ll l=0,r=0;
        if(i<=n){
            while(--d[i]) rt[i]=pop(rt[i]);
            r=v[rt[i]],rt[i]=pop(rt[i]);
            l=v[rt[i]],rt[i]=pop(rt[i]);
        }
        v[++tot]=l+w[i],v[++tot]=r+w[i];
        rt[i]=merge(rt[i],merge(tot,tot-1));
        rt[fa[i]]=merge(rt[fa[i]],rt[i]);
    }
    while(d[1]--) rt[1]=pop(rt[1]);
    while(rt[1]) sum-=v[rt[1]],rt[1]=pop(rt[1]);
    printf("%lld\n",sum);
    return 0;
}