C++之路进阶——最小费用最大流（支线剧情）

 1 #include <cstdio>  
 2 #include <cstring>  
 3 #include<queue>
 4 #include <iostream>  
 5 #include <algorithm>  
 6 #define maxn 310  
 7 #define S 0  
 8 #define T (n+1)  
 9   
10 using namespace std;
11   
12 int ans=0,n,m;
13   
14 namespace Min_Cost_Max_Flow
15    {
16       int head[maxn],from[maxn],dis[maxn],inq[maxn],cnt=1; 
17       
18       struct ss
19         {
20             int c;
21             int v;
22             int next;
23             int to;
24             int from;
25         }e[1001001];
26       void add(int u,int v,int w,int c)
27            {
28              e[++cnt].next=head[u];
29              e[cnt].v=w;
30              e[cnt].c=c;
31              e[cnt].from=u;
32              head[u]=cnt;
33              e[cnt].to=v;
34            }
35      void  insert(int u,int v,int w,int c)
36            {
37              add(u,v,w,c);
38              add(v,u,0,-c);
39            }
40      bool spfa()
41            {
42              for (int i=1;i<=T;i++) dis[i]=0x7fffffff;
43              dis[S]=0;
44              inq[S]=0;
45              queue<int>que;
46              que.push(S);
47              while (!que.empty())
48                {
49                   int now=que.front();
50                   que.pop();
51                   inq[now]=0;
52                   for (int i=head[now];i;i=e[i].next)
53                      if (e[i].v&&dis[e[i].to]>dis[now]+e[i].c)
54                         {
55                             dis[e[i].to]=dis[now]+e[i].c;
56                             from[e[i].to]=i;
57                             if (!inq[e[i].to]) inq[e[i].to]=1,que.push(e[i].to);                
58                         }
59                }
60             if (dis[T]==0x7fffffff) return 0; 
61                return 1;      
62            }              
63      void mcf()
64            {
65              int x=0x7fffffff;
66              for (int i=from[T];i;i=from[e[i].from])
67                 x=min(x,e[i].v);
68              for (int i=from[T];i;i=from[e[i].from])
69                 {
70                     e[i].v-=x;
71                     e[i^1].v+=x;
72                     ans+=x*e[i].c;
73                 }    
74            }           
75     }
76  int main()
77      {
78         using namespace Min_Cost_Max_Flow;
79          scanf("%d",&n); 
80         for (int i=1;i<=n;i++)
81           {
82             int k;
83             scanf("%d",&k);
84             insert(i,T,k,0);
85             for (int j=1;j<=k;j++)
86               {
87                 int y,z;
88                 scanf("%d%d",&y,&z);
89                 insert(i,y,0x7fffffff,z);
90                 insert(S,y,1,z);    
91               } 
92             if (i!=1) insert(i,1,0x7fffffff,0);   
93           }
94         while (spfa()) mcf();
95          printf("%d\n",ans);  
96      }