[hdu6598]Harmonious Army

网络流建图,首先将所有价值加起来,用最小割考虑要删掉多少个价值:源点向每一个士兵连流量为x的边,士兵向汇点连流量为y的边,每一对关系间连流量为z的边,考虑有方程x1+y2+z=x2+y1+z=a+c,x1+x2=b+c,y1+y2=a+b,由于对称性(其实也不一定要对称),解得x1=x2=(b+c)/2,y1=y2=(a+b)/2,z=(a+c)/2-b,把边都乘以2用总价值减去最大流除以2就可以得到答案

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 #define N 505
 4 #define ll long long
 5 struct ji{
 6     int nex,to,len;
 7 }edge[N*N];
 8 queue<int>q;
 9 int E,n,m,x,y,a,b,c,d[N],head[N],work[N];
10 void add(int x,int y,int z){
11     edge[E].nex=head[x];
12     edge[E].to=y;
13     edge[E].len=z;
14     head[x]=E++;
15     if (E&1)add(y,x,0); 
16 }
17 bool bfs(){
18     q.push(0);
19     for(int i=0;i<=n+1;i++)d[i]=-1;
20     d[0]=0;
21     while (!q.empty()){
22         int k=q.front();
23         q.pop();
24         for(int i=head[k];i!=-1;i=edge[i].nex)
25             if ((edge[i].len)&&(d[edge[i].to]<0)){
26                 d[edge[i].to]=d[k]+1;
27                 q.push(edge[i].to);
28             }
29     }
30     return d[n+1]>=0;
31 }
32 int dfs(int k,int s){
33     if (k>n)return s;
34     int p;
35     for(int &i=work[k];i!=-1;i=edge[i].nex)
36         if ((edge[i].len)&&(d[edge[i].to]==d[k]+1)){
37             p=dfs(edge[i].to,min(s,edge[i].len));
38             if (p){
39                 edge[i].len-=p;
40                 edge[i^1].len+=p;
41                 return p;
42             }
43         }
44     return 0;
45 }
46 ll dinic(){
47     int k=0;
48     ll ans=0;
49     while (bfs()){
50         for(int i=0;i<=n+1;i++)work[i]=head[i];
51         while (k=dfs(0,0x3f3f3f3f))ans+=k;
52     }
53     return ans;
54 }
55 int main(){
56     while (scanf("%d%d",&n,&m)!=EOF){
57         for(int i=0;i<=n+1;i++)head[i]=-1;
58         ll ans=E=0;
59         for(int i=1;i<=m;i++){
60             scanf("%d%d%d%d%d",&x,&y,&a,&b,&c);
61             add(0,x,b+c);
62             add(0,y,b+c);
63             add(x,n+1,a+b);
64             add(y,n+1,a+b);
65             add(x,y,a+c-2*b);
66             add(y,x,a+c-2*b);
67             ans+=a+b+c;
68         }
69         printf("%lld\n",ans-dinic()/2);
70     }
71 }
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转载自www.cnblogs.com/PYWBKTDA/p/11260554.html