BZOJ 2424: [HAOI2010]订货（费用流）

裸的费用流了= =从源点向每个点连费用为di，从汇点向每个点连流量为ui，每个点向下一个点连费用为m，流量为s的边就行了

CODE：

#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cstring>
#include<queue>
using namespace std;
#define maxn 65
#define maxm 400
#define inf 0x7fffffff
struct edges{
 int to,next,cap,dist;
}edge[maxm];
int next[maxn],l;
int s,t;
int addedge(int x,int y,int z,int cap){
 l++;
 edge[l*2]=(edges){y,next[x],cap,z};
 edge[l*2+1]=(edges){x,next[y],0,-z};
 next[x]=l*2;next[y]=l*2+1;
 return 0;
}
int dist[maxn],way[maxn];
bool b[maxn];
queue<int> q;
bool spfa(){
 for (int i=1;i<=t;i++) dist[i]=inf;
 dist[s]=0;
 q.push(s);
 while (!q.empty()){
  int u=q.front();q.pop();
  b[u]=0;
  for (int i=next[u];i;i=edge[i].next)
   if (edge[i].cap&&dist[edge[i].to]>dist[u]+edge[i].dist){
    dist[edge[i].to]=dist[u]+edge[i].dist;
    way[edge[i].to]=i;
    if(!b[edge[i].to]){
     b[edge[i].to]=1;
     q.push(edge[i].to);
    }
   }
 }
 if (dist[t]==inf) return 0;
 return 1;
}
int mcmf(){
 int cost=0;
 while (spfa()){
  int flow=inf,x=t;
  while (x!=s){
   flow=min(flow,edge[way[x]].cap);
   x=edge[way[x]^1].to;
  }
  cost+=dist[t]*flow;
  x=t;
  while (x!=s){
   edge[way[x]].cap-=flow;
   edge[way[x]^1].cap+=flow;
   x=edge[way[x]^1].to;
  }
 }
 return cost;
}
int main(){
 int n,m,S;
 scanf("%d%d%d",&n,&m,&S);
 s=n+1;t=n+2;
 for (int i=1;i<n;i++) addedge(i,i+1,m,S);
 for (int i=1;i<=n;i++) {
  int x;
  scanf("%d",&x);
  addedge(i,t,0,x);
 }
 for (int i=1;i<=n;i++) {
  int x;
  scanf("%d",&x);
  addedge(s,i,x,inf);
 }
 printf("%d",mcmf());
 return 0;
}