POJ2047 Concert Hall Scheduling（最小费用最大流）

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<queue>
 4 #include<algorithm>
 5 using namespace std;
 6 #define INF (1<<30)
 7 #define MAXN 1111
 8 #define MAXM 1111*1111*2
 9 struct Edge{
10     int u,v,cap,cost,next;
11 }edge[MAXM];
12 int vs,vt,NV,NE,head[MAXN];
13 void addEdge(int u,int v,int cap,int cost){
14     edge[NE].u=u; edge[NE].v=v;
15     edge[NE].cap=cap; edge[NE].cost=cost;
16     edge[NE].next=head[u]; head[u]=NE++;
17     edge[NE].u=v; edge[NE].v=u;
18     edge[NE].cap=0; edge[NE].cost=-cost;
19     edge[NE].next=head[v]; head[v]=NE++;
20 }
21 int d[MAXN],pre[MAXN];
22 bool vis[MAXN];
23 bool SPFA(){
24     for(int i=0; i<NV; ++i){
25         d[i]=INF; vis[i]=0;
26     }
27     d[vs]=0; vis[vs]=1;
28     queue<int> que;
29     que.push(vs);
30     while(!que.empty()){
31         int u=que.front(); que.pop();
32         for(int i=head[u]; i!=-1; i=edge[i].next){
33             int v=edge[i].v;
34             if(edge[i].cap && d[v]>d[u]+edge[i].cost){
35                 d[v]=d[u]+edge[i].cost;
36                 pre[v]=i;
37                 if(!vis[v]){
38                     vis[v]=1;
39                     que.push(v);
40                 }
41             }
42         }
43         vis[u]=0;
44     }
45     return d[vt]!=INF;
46 }
47 int MCMF(){
48     int res=0;
49     while(SPFA()){
50         int flow=INF,cost=0;
51         for(int u=vt; u!=vs; u=edge[pre[u]].u){
52             flow=min(flow,edge[pre[u]].cap);
53         }
54         for(int u=vt; u!=vs; u=edge[pre[u]].u){
55             edge[pre[u]].cap-=flow;
56             edge[pre[u]^1].cap+=flow;
57             cost+=flow*edge[pre[u]].cost;
58         }
59         res+=cost;
60     }
61     return res;
62 }
63 int x[1111],y[1111],w[1111],point[2222],pn;
64 int getposi(int a){
65     return lower_bound(point,point+pn,a)-point;
66 }
67 int main(){
68     int n;
69     while(~scanf("%d",&n) && n){
70         pn=0;
71         for(int i=0; i<n; ++i){
72             scanf("%d%d%d",x+i,y+i,w+i);
73             point[pn++]=x[i];
74             point[pn++]=++y[i];
75         }
76         sort(point,point+pn);
77         pn=unique(point,point+pn)-point;
78         vs=pn; vt=vs+1; NV=vt+1; NE=0;
79         memset(head,-1,sizeof(head));
80         addEdge(vs,0,2,0); addEdge(pn-1,vt,2,0);
81         for(int i=1; i<pn; ++i){
82             addEdge(i-1,i,INF,0);
83         }
84         for(int i=0; i<n; ++i){
85             addEdge(getposi(x[i]),getposi(y[i]),1,-w[i]);
86         }
87         printf("%d\n",-MCMF());
88     }
89     return 0;
90 }