餐巾计划问题

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<algorithm>
#include<cstring>
#include<queue>
#include<stack>
#include<ctime>
#include<vector>
using namespace std;
int n,m;
struct node
{
    int next,to;
    long long cap,cost;
}edge[400001];
int sze=1,head[5001];
long long a[5001];
void putin(int from,int to,long long cap,long long cost)
{
    sze++;
    edge[sze].to=to;
    edge[sze].cap=cap;
    edge[sze].cost=cost;
    edge[sze].next=head[from];
    head[from]=sze;
}
void in(int from,int to,long long cap,long long cost)
{
    putin(from,to,cap,cost);
    putin(to,from,0,-cost);
}
long long ans,f[5001];
int pre[5001],vis[5001];
bool bfs(int src,int des)
{
    int i;
    for(i=0;i<=n*2+1;i++){f[i]=1e18;vis[i]=0;}
    queue<int>mem;
    mem.push(src);
    f[src]=0;vis[i]=1;
    while(!mem.empty())
    {
        int x=mem.front();mem.pop();
        vis[x]=0;
        for(i=head[x];i!=-1;i=edge[i].next)
        {
            int y=edge[i].to;
            if(edge[i].cap&&f[y]>f[x]+edge[i].cost)
            {
                f[y]=f[x]+edge[i].cost;
                pre[y]=i;
                if(!vis[y]){mem.push(y);vis[y]=1;}
            }
        }
    }
    if(f[des]==1e18)return 0;
    else return 1;
}
void change(int src,int des)
{
    int x=des;
    long long flow=1e18;
    while(x!=src)
    {
        flow=min(flow,edge[pre[x]].cap);
        x=edge[pre[x]^1].to;
    }
    x=des;
    while(x!=src)
    {
        ans+=flow*edge[pre[x]].cost;
        edge[pre[x]].cap-=flow;
        edge[pre[x]^1].cap+=flow;
        x=edge[pre[x]^1].to;
    }
}
void mincostflow(int src,int des)
{
    while(bfs(src,des))change(src,des);
}
int main()
{
    int i,j;
    scanf("%d",&n);
    memset(head,-1,sizeof(head));
    long long s,d1,c1,d2,c2;
    scanf("%lld%lld%lld%lld%lld",&s,&d1,&c1,&d2,&c2);
    for(i=1;i<=n;i++)scanf("%lld",&a[i]);
    for(i=1;i<=n;i++)
    {
        if(i>=2)in(i+n-1,i+n,2e8,0);
        in(0,i,a[i],0);
        in(0,n+i,a[i],s);
        if(i+d1<=n)in(i,i+n+d1,a[i],c1);
        if(i+d2<=n)in(i,i+n+d2,a[i],c2);
        in(n+i,n*2+1,a[i],0);
    }
    mincostflow(0,n*2+1);
    cout<<ans;
    return 0;
}