洛谷P3381 【模板】最小费用最大流

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费用流板子

细节真多……一个边的flow和点的flow分不清……还有往回减流的时候应该减去flow[t]……

 1 //minamoto
 2 #include<iostream>
 3 #include<cstdio>
 4 #include<queue>
 5 #include<algorithm>
 6 #include<cstring>
 7 using namespace std;
 8 #define getc() (p1==p2&&(p2=(p1=buf)+fread(buf,1,1<<21,stdin),p1==p2)?EOF:*p1++)
 9 char buf[1<<21],*p1=buf,*p2=buf;
10 inline int read(){
11     #define num ch-'0'
12     char ch;bool flag=0;int res;
13     while(!isdigit(ch=getc()))
14     (ch=='-')&&(flag=true);
15     for(res=num;isdigit(ch=getc());res=res*10+num);
16     (flag)&&(res=-res);
17     #undef num
18     return res;
19 }
20 const int N=5005,M=100005;
21 bool vis[N];
22 int n,m,s,t,u,v,e,f,dis[N],Pre[N],last[N],disf[N],maxflow,mincost;
23 int head[N],Next[M],ver[M],edge[M],flow[M],tot=1;
24 queue<int> q;
25 inline void add(int u,int v,int f,int e){
26     ver[++tot]=v,Next[tot]=head[u],head[u]=tot,edge[tot]=e,flow[tot]=f;
27     ver[++tot]=u,Next[tot]=head[v],head[v]=tot,edge[tot]=-e,flow[tot]=0;
28 }
29 bool spfa(){
30     memset(dis,0x3f,sizeof(dis));
31     memset(disf,0x3f,sizeof(disf));
32     memset(vis,0,sizeof(vis));
33     q.push(s),vis[s]=1,dis[s]=0,Pre[t]=-1;
34     while(!q.empty()){
35         int u=q.front();q.pop();vis[u]=0;
36         for(int i=head[u];i;i=Next[i]){
37             int v=ver[i];
38             if(flow[i]>0&&dis[v]>dis[u]+edge[i]){
39                 dis[v]=dis[u]+edge[i];
40                 Pre[v]=u;
41                 last[v]=i;
42                 disf[v]=min(disf[u],flow[i]);
43                 if(!vis[v]){
44                     vis[v]=1,q.push(v);
45                 }
46             }
47         }
48     }
49     return Pre[t]!=-1;
50 }
51 void MCMF(){
52     while(spfa()){
53         int u=t;
54         maxflow+=disf[t];
55         mincost+=disf[t]*dis[t];
56         while(u!=s){
57             flow[last[u]]-=disf[t];
58             flow[last[u]^1]+=disf[t];
59             u=Pre[u];
60         }
61     }
62 }
63 int main(){
64     n=read(),m=read(),s=read(),t=read();
65     for(int i=1;i<=m;++i){
66         u=read(),v=read(),f=read(),e=read();
67         add(u,v,f,e);
68     }
69     MCMF();
70     printf("%d %d\n",maxflow,mincost);
71     return 0;
72 }