「luogu1251」餐巾计划问题 

建图很巧妙。

 1 #include<bits/stdc++.h>
 2 #define ll long long
 3 using namespace std;
 4 const int N=4010;
 5 const ll oo=3e18;
 6 int tot,n,m,f,s,p,super_s,super_t;
 7 struct Edge{
 8     int from,to;
 9     ll flow,cap,cost;
10     Edge(int _from=0,int _to=0,ll _flow=0,ll _cap=0,ll _cost=0):from(_from),to(_to),flow(_flow),cap(_cap),cost(_cost){}
11 };
12 Edge edge[40010];
13 vector<int>point[N];
14 int edge_tot;
15 void add_edge(int f,int t,ll c,ll cc){
16     edge[edge_tot]=Edge(f,t,0,c,cc);
17     point[f].push_back(edge_tot++);
18     edge[edge_tot]=Edge(t,f,0,0,-cc);
19     point[t].push_back(edge_tot++);
20     return;
21 }
22 ll dis[N];
23 int pre[N];
24 bool inq[N];
25 bool spfa(){
26     memset(dis,127/2,sizeof(dis));
27     queue<int>q;
28     q.push(super_s);
29     dis[super_s]=0,inq[super_s]=1;
30     int x;
31     while(!q.empty()){
32         x=q.front();q.pop();
33         inq[x]=0;
34         for(int i=0;i<point[x].size();i++){
35             Edge& e=edge[point[x][i]];
36             if(e.cap<=e.flow) continue;
37             if(dis[e.to]>dis[x]+e.cost){
38                 dis[e.to]=dis[x]+e.cost,pre[e.to]=point[x][i];
39                 if(!inq[e.to]){q.push(e.to);inq[e.to]=1;}
40             }
41         }
42     }
43     return dis[super_t]<oo;
44 }
45 ll mincostflow(){
46     int now;
47     ll minf,ans=0;
48     while(spfa()){
49         minf=oo,now=super_t;
50         while(now!=super_s) minf=min(minf,edge[pre[now]].cap-edge[pre[now]].flow),now=edge[pre[now]].from;
51         now=super_t,ans+=1LL*minf*dis[super_t];
52         while(now!=super_s) edge[pre[now]].flow+=minf,edge[pre[now]^1].flow-=minf,now=edge[pre[now]].from;
53     }
54     return ans;
55 }
56 int main(){
57     int t1;
58     scanf("%d",&tot);
59     super_s=tot+tot+1,super_t=tot+tot+2;
60     for(int i=1;i<=tot;i++){
61         scanf("%d",&t1);
62         add_edge(super_s,i,t1,0);
63         add_edge(i+tot,super_t,t1,0);
64         if(i<tot) add_edge(i+tot,i+tot+1,oo,0);
65     }
66     scanf("%d%d%d%d%d",&p,&m,&f,&n,&s);
67     for(int i=1;i<=tot-m;i++) add_edge(i,i+m+tot,oo,f);
68     for(int i=1;i<=tot-n;i++) add_edge(i,i+n+tot,oo,s);
69     for(int i=1;i<=tot;i++) add_edge(super_s,i+tot,oo,p);
70     printf("%lld",mincostflow());
71     return 0;
72 }

 

posted @ 2018-03-08 13:17  Cupcake  阅读(135)  评论(0)    收藏  举报