[BZOJ 1221][HNOI2001] 软件开发：费用流

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建议看这里http://www.acyume.com/archives/1069

/*
User:Small
Language:C++
Problem No.:1221
*/
#include<bits/stdc++.h>
#define ll long long
#define inf 999999999
using namespace std;
const int N=2005,M=20005;
int n,a,b,f,fa,fb,fir[N],tot=1,ans,dis[N];
bool vis[N];
struct edge{
    int v,w,c,nex;
}e[M];
void add(int u,int v,int w,int c){
    e[++tot]=(edge){v,w,c,fir[u]};
    fir[u]=tot;
    e[++tot]=(edge){u,0,-c,fir[v]};
    fir[v]=tot;
}
bool spfa(int s,int t){
    memset(vis,0,sizeof(vis));
    memset(dis,127,sizeof(dis));
    dis[t]=0;
    vis[t]=1;
    queue<int> q;
    q.push(t);
    while(!q.empty()){
        int u=q.front();
        q.pop();
        vis[u]=0;
        for(int i=fir[u];i;i=e[i].nex){
            int v=e[i].v;
            if(e[i^1].w&&dis[v]>dis[u]+e[i^1].c){
                dis[v]=dis[u]+e[i^1].c;
                if(!vis[v]){
                    vis[v]=1;
                    q.push(v);
                }
            }
        }
    }
    return dis[s]<inf;
}
int dfs(int u,int f,int t){
    vis[u]=1;
    if(u==t) return f;
    int sum=0;
    for(int i=fir[u];i;i=e[i].nex){
        int v=e[i].v;
        if(!vis[v]&&e[i].w&&dis[v]+e[i].c==dis[u]){
            int d=dfs(v,min(f,e[i].w),t);
            ans+=d*e[i].c;
            e[i].w-=d;
            e[i^1].w+=d;
            f-=d;
            sum+=d;
            if(!f) return sum;
        }
    }
    return sum;
}
void zkw(int s,int t){
    while(spfa(s,t)){
        vis[t]=1;
        while(vis[t]){
            memset(vis,0,sizeof(vis));
            dfs(s,inf,t);
        }
    }
}
int main(){
    freopen("data.in","r",stdin);//
    scanf("%d%d%d%d%d%d",&n,&a,&b,&f,&fa,&fb);
    for(int i=1;i<=n;i++){
        int x;
        scanf("%d",&x);
        add(1,i+n+2,inf,f);
        add(1,i+2,x,0);
        add(i+2+n,2,x,0);
        if(i+a+1<=n) add(i+2,i+n+3+a,inf,fa);
        if(i+b+1<=n) add(i+2,i+n+3+b,inf,fb);
        if(i<n) add(i+2,i+3,inf,0);
    }
    zkw(1,2);
    printf("%d\n",ans);
    return 0;
}