AC日记——餐巾计划问题 洛谷 P1084

#include <bits/stdc++.h>
using namespace std;
#define maxn 4005
#define maxque 1000005
#define INF 0x7fffffff
#define ll long long
ll n,head[maxn],E[maxque],V[maxque],W[maxque],F[maxque];
ll pi,qt,qc,st,sc,s,t,cnt=1,day[maxn],pre[maxn],dis[maxn];
ll que[maxque],ans;
bool if_[maxn];
inline void in(ll &now)
{
    char Cget=getchar();now=0;
    while(Cget>‘9‘||Cget<‘0‘) Cget=getchar();
    while(Cget>=‘0‘&&Cget<=‘9‘)
    {
        now=now*10+Cget-‘0‘;
        Cget=getchar();
    }
}
inline void edge_add(ll u,ll v,ll w,ll f)
{
    E[++cnt]=head[u],V[cnt]=v,W[cnt]=w,F[cnt]=f,head[u]=cnt;
    E[++cnt]=head[v],V[cnt]=u,W[cnt]=-w,F[cnt]=0,head[v]=cnt;
}
bool spfa()
{
    for(ll i=s;i<=t;i++)dis[i]=INF,if_[i]=false,pre[i]=-1;
    ll h=maxque>>1,tail=h+1,now;que[h]=s,if_[s]=true,dis[s]=0;
    while(h<tail)
    {
        now=que[h++],if_[now]=false;
        for(ll i=head[now];i;i=E[i])
        {
            if(F[i]>0&&W[i]+dis[now]<dis[V[i]])
            {
                pre[V[i]]=i,dis[V[i]]=dis[now]+W[i];
                if(!if_[V[i]])
                {
                    if(dis[V[i]]<=dis[que[h]]&&h<tail) que[--h]=V[i];
                    else que[tail++]=V[i];
                    if_[V[i]]=true;
                }
            }
        }
    }
    return dis[t]!=INF;
}
int main()
{
    in(n),s=0,t=n*2+1;ll pos,now;
    for(ll i=1;i<=n;i++)in(day[i]);
    in(pi),in(qt),in(qc),in(st),in(sc);
    for(ll i=1;i<=n;i++)
    {
        edge_add(s,i,pi,INF);
        edge_add(i,t,0,day[i]);
        edge_add(s,i+n,0,day[i]);
        if(i+qt<=n) edge_add(i+n,i+qt,qc,INF);
        if(i+st<=n) edge_add(i+n,i+st,sc,INF);
        if(i!=n) edge_add(i+n,i+n+1,0,INF);
    }
    while(spfa())
    {
        now=t,pos=INF;
        while(pre[now]!=-1)
        {
            pos=min(pos,F[pre[now]]);
            now=V[pre[now]^1];
        }
        now=t,ans+=dis[t]*pos;
        while(pre[now]!=-1)
        {
            F[pre[now]]-=pos;
            F[pre[now]^1]+=pos;
            now=V[pre[now]^1];
        }
    }
    printf("%lld\n",ans);
    return 0;
}