BZOJ 2424 订货

Posted 2020-08-12 ziliuziliu

费用流。

#include<iostream>
#include<cstdio>
#include<queue>
#include<cstring>
#include<algorithm>
#define maxv 250
#define maxe 1000050
#define inf 2000000000
using namespace std;
int n,m,S,u[maxv],d[maxv],nume=1,g[maxv],dis[maxv],pree[maxv],prev[maxv],s,t;
queue <int> q;
bool vis[maxv];
struct edge
{
    int v,f,c,nxt;
}e[maxe];
void addedge(int u,int v,int f,int c)
{
    e[++nume].v=v;e[nume].f=f;e[nume].c=c;e[nume].nxt=g[u];g[u]=nume;
    e[++nume].v=u;e[nume].f=0;e[nume].c=-c;e[nume].nxt=g[v];g[v]=nume;
}
void build()
{
    s=0;t=2*n+1;
    for (int i=1;i<=n;i++)
    {
        addedge(s,i,inf,d[i]);
        addedge(i,i+n,inf,0);
        addedge(i+n,t,u[i],0);
    }
    for (int i=1;i<=n-1;i++)
        addedge(i+n,i+1,S,m);
}
bool spfa()
{
    for (int i=s;i<=t;i++) {pree[i]=prev[i]=-1;dis[i]=inf;vis[i]=false;}
    q.push(s);vis[s]=true;dis[s]=0;
    while (!q.empty())
    {
        int head=q.front();q.pop();
        for (int i=g[head];i;i=e[i].nxt)
        {
            int v=e[i].v;
            if ((e[i].f) && (dis[v]>dis[head]+e[i].c))
            {
                dis[v]=dis[head]+e[i].c;
                pree[v]=i;prev[v]=head;
                if (!vis[v]) {q.push(v);vis[v]=true;}
            }
        }
        vis[head]=false;
    }
    if (dis[t]==inf) return false;
    return true;
}
int dinic()
{
    int u=t,low=inf;
    while (u!=s)
    {
        low=min(low,e[pree[u]].f);
        u=prev[u];
    }
    u=t;
    while (u!=s)
    {
        e[pree[u]].f-=low;e[pree[u]^1].f+=low;
        u=prev[u];
    }
    return dis[t]*low;
}
int main()
{
    scanf("%d%d%d",&n,&m,&S);
    for (int i=1;i<=n;i++) scanf("%d",&u[i]);
    for (int i=1;i<=n;i++) scanf("%d",&d[i]);
    build();
    int min_cost=0;
    while (spfa()) min_cost+=dinic();
    printf("%d\n",min_cost);
    return 0;
}