[UOJ] #217. 【UNR #1】奇怪的线段树

题解见大佬博客

我的丑陋代码：

#include<cstdio>
#include<cstring>
#include<cstdlib>
inline int read()
{
    int x;char c;
    while((c=getchar())<''||c>'');
    for(x=c-'';(c=getchar())>=''&&c<='';)x=x*+c-'';
    return x;
}
#define MN 8000
#define MV 16000
#define ME 56000
#define INF 0x3FFFFFFF
struct edge{int nx,t,l,w;}e[ME*+];
int S=MV+,T=MV+,h[MV+],en=,d[MV+],q[MV+],qn,c[MV+];
int cnt=,L[MN+],R[MN+],u[MN+],z[MN+],fa[MN+];
inline void ins(int x,int y,int l,int w)
{
    e[++en]=(edge){h[x],y,l,w};h[x]=en;
    e[++en]=(edge){h[y],x,,};h[y]=en;
}
bool build(int k,int l,int r)
{
    u[k]=read();
    if(k>&&u[k]&&!u[fa[k]])exit(*puts("OwO"));
    if(l<r)
    {
        int mid;
        fa[L[k]=++cnt]=k;build(L[k],l,mid=read());
        fa[R[k]=++cnt]=k;build(R[k],mid+,r);
        z[L[k]]=R[k];
        ins(k,L[k],,INF);
    }
    L[k]=l;R[k]=r;
}
bool bfs()
{
    int i,j;
    memset(d,,sizeof(d));
    for(d[q[i=qn=]=S]=;i<=qn;++i)for(j=c[q[i]]=h[q[i]];j;j=e[j].nx)
        if(e[j].w&&!d[e[j].t])d[q[++qn]=e[j].t]=d[q[i]]+;
    return d[T];
}
int dfs(int x,int r)
{
    if(x==T)return r;
    int k,u=;
    for(int&i=c[x];i;i=e[i].nx)if(e[i].w&&d[e[i].t]==d[x]+)
    {
        k=dfs(e[i].t,r-u<e[i].w?r-u:e[i].w);
        u+=k;e[i].w-=k;e[i^].w+=k;
        if(u==r)return u;
    }
    return d[x]=,u;
}
int main()
{
    int n=read(),i,j;
    build(,,n);
    for(i=;i<*n;++i)if(u[i])
    {
        ins(S,i,,INF);
        for(j=i;++j<*n;)if(L[i]<=L[j]&&R[i]>=R[j]&&u[j])u[i]=;
        ins(i,i+*n,u[i],INF);
        ins(i+*n,T,,INF);
        for(j=i;++j<*n;)if(R[i]+==L[j]&&z[i]!=j){ins(i+*n,j,,INF);break;}
    }
    for(i=;i<=T;++i)for(j=h[i];j;j=e[j].nx)d[i]-=e[j].l,d[e[j].t]+=e[j].l,e[j].w-=e[j].l;
    for(S+=,T+=,i=;i<S;++i)
    {
        if(d[i]<)ins(i,T,,-d[i]);
        if(d[i]>)ins(S,i,,d[i]);
    }
    while(bfs())dfs(S,INF);
    ins(T-,S-,,INF);
    while(bfs())dfs(S,INF);
    for(i=h[S-];i;i=e[i].nx)if(e[i].t==T-)printf("%d",e[i].w);
}