[haoi2010]订货 最小费用流

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstdlib>
 4 #include<cstring>
 5 #include<string>
 6 using namespace std;
 7 const int maxn=500;
 8 const int inf=10000000;
 9 const int S=0,T=50+1;
10 struct node{
11     int x,y,next,flow,v,re;
12 }e[maxn];
13 int linkk[maxn],len=0,n,m,s,u[maxn],c[maxn];
14 void insert(int x,int y,int flow,int v){
15     e[++len].x=x;
16     e[len].y=y;
17     e[len].v=v;
18     e[len].flow=flow;
19     e[len].next=linkk[x];
20     e[len].re=len+1;
21     linkk[x]=len;
22     e[++len].x=y;
23     e[len].y=x;
24     e[len].flow=0;
25     e[len].v=v;
26     e[len].next=linkk[y];
27     e[len].re=len-1;
28     linkk[y]=len;
29 }
30 void init(){
31     scanf("%d%d%d",&n,&m,&s);
32     for(int i=1;i<=n;i++)scanf("%d",&u[i]);
33     for(int i=1;i<=n;i++)scanf("%d",&c[i]);
34     for(int i=1;i<=n;i++){
35         insert(S,i,inf,c[i]);insert(i,T,u[i],0);
36     }
37     for(int i=1;i<n;i++)insert(i,i+1,s,m);
38 }
39 int vis[maxn],d[maxn],q[maxn*maxn],head=0,tail=0,pre[maxn],ans=0,cap[maxn],t[maxn];
40 bool SPFA(){
41     for(int i=S;i<=T;i++)d[i]=inf<<2;
42     memset(vis,0,sizeof(vis));
43     head=0,tail=0;
44     q[++tail]=S;d[S]=0;
45     while(++head<=tail){
46         int x=q[head];
47         vis[x]=0;
48         for(int i=linkk[x];i;i=e[i].next){
49             if(e[i].flow&&d[e[i].y]>d[x]+e[i].v){
50                 d[e[i].y]=d[x]+e[i].v;
51                 cap[e[i].y]=e[i].flow;
52                 t[e[i].y]=i;
53                 pre[e[i].y]=x;
54                 if(!vis[e[i].y]){
55                     vis[e[i].y]=1;
56                     q[++tail]=e[i].y;
57                 }
58             }
59         }
60     }
61     if(d[T]==inf<<2)return 0;
62     int flow=inf;
63     for(int i=T;i!=S;i=pre[i])flow=min(flow,cap[i]);
64     for(int i=T;i!=S;i=pre[i]){
65         e[t[i]].flow-=flow;
66         e[e[t[i]].re].flow+=flow;
67         ans+=e[t[i]].v*flow;
68     }
69     return 1;
70 }
71 void work(){
72     ans=0;
73     while(SPFA());
74     cout<<ans<<endl;
75 }
76 int main(){
77     init();
78     work();
79 }