[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())<'0'||c>'9');
    for(x=c-'0';(c=getchar())>='0'&&c<='9';)x=x*10+c-'0';
    return x;
}
#define MN 8000
#define MV 16000
#define ME 56000
#define INF 0x3FFFFFFF
struct edge{int nx,t,l,w;}e[ME*2+5];
int S=MV+1,T=MV+2,h[MV+5],en=1,d[MV+5],q[MV+5],qn,c[MV+5];
int cnt=1,L[MN+5],R[MN+5],u[MN+5],z[MN+5],fa[MN+5];
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,0,0};h[y]=en;
}
bool build(int k,int l,int r)
{
    u[k]=read();
    if(k>1&&u[k]&&!u[fa[k]])exit(0*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+1,r);
        z[L[k]]=R[k];
        ins(k,L[k],0,INF);
    }
    L[k]=l;R[k]=r;
}
bool bfs()
{
    int i,j;
    memset(d,0,sizeof(d));
    for(d[q[i=qn=0]=S]=1;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]]+1;
    return d[T];
}
int dfs(int x,int r)
{
    if(x==T)return r;
    int k,u=0;
    for(int&i=c[x];i;i=e[i].nx)if(e[i].w&&d[e[i].t]==d[x]+1)
    {
        k=dfs(e[i].t,r-u<e[i].w?r-u:e[i].w);
        u+=k;e[i].w-=k;e[i^1].w+=k;
        if(u==r)return u;
    }
    return d[x]=0,u;
}
int main()
{
    int n=read(),i,j;
    build(1,1,n);
    for(i=1;i<2*n;++i)if(u[i])
    {
        ins(S,i,0,INF);
        for(j=i;++j<2*n;)if(L[i]<=L[j]&&R[i]>=R[j]&&u[j])u[i]=0;
        ins(i,i+2*n,u[i],INF);
        ins(i+2*n,T,0,INF);
        for(j=i;++j<2*n;)if(R[i]+1==L[j]&&z[i]!=j){ins(i+2*n,j,0,INF);break;}
    }
    for(i=1;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+=2,T+=2,i=1;i<S;++i)
    {
        if(d[i]<0)ins(i,T,0,-d[i]);
        if(d[i]>0)ins(S,i,0,d[i]);
    }
    while(bfs())dfs(S,INF);
    ins(T-2,S-2,0,INF);
    while(bfs())dfs(S,INF);
    for(i=h[S-2];i;i=e[i].nx)if(e[i].t==T-2)printf("%d",e[i].w);
}