网络流-最大流 Dinic模板

Posted 2020-10-30 weeping

 1 #include <bits/stdc++.h>
 2 
 3 using namespace std;
 4 
 5 #define MP make_pair
 6 #define PB push_back
 7 #define ls first
 8 #define rs second
 9 typedef long long LL;
10 typedef pair<int,int> PII;
11 const double eps=1e-8;
12 const double pi=acos(-1.0);
13 const int K=1e5+7;
14 const int mod=1e9+7;
15 
16 vector<pair<int,int>>mp[K];
17 int n,m,cnt,flow[K*2],deep[K],cur[K];  
18 
19 int bfs(int s,int t)
20 {
21     queue<int>q;
22     memset(deep,0,sizeof deep);
23     q.push(s),deep[s]=1;
24     while(!q.empty())
25     {
26         int u=q.front();q.pop();
27         for(auto &it:mp[u])
28         if(!deep[it.ls]&&flow[it.rs])
29         {
30             deep[it.ls]=deep[u]+1;
31             q.push(it.ls);
32             if(it.ls==t)
33                 return 1;
34         }
35     }
36     return 0;
37 }
38 int dfs(int x,int d,int t)
39 {
40     if(x==t) return d;
41     for(int i=cur[x];i<mp[x].size();cur[x]=++i)
42     {
43         int u=mp[x][i].ls,v=mp[x][i].rs;
44         if(deep[u]==deep[x]+1&&flow[v])
45         {
46             int td=min(d,dfs(u,min(d,flow[v]),t));
47             if(!td) continue;
48             flow[v]-=td;
49             flow[v^1]+=td;
50             return td;
51         }
52     }
53     return 0;
54 }
55 int dinic(int s,int t)
56 {
57     int ret=0,d;
58     while(bfs(s,t))
59     {
60         memset(cur,0,sizeof cur);
61         while(d=dfs(s,mod,t))    ret+=d;
62     }
63     return ret;
64 }
65 int main(void)
66 {
67     while(~scanf("%d%d",&m,&n))
68     {
69         cnt=0;
70         memset(mp,0,sizeof mp);
71         for(int i=0,u,v,w;i<m;i++)
72         {
73             scanf("%d%d%d",&u,&v,&w);
74             flow[cnt]=w,flow[cnt+1]=0;
75             mp[u].PB(MP(v,cnt++));
76             mp[v].PB(MP(u,cnt++));
77         }
78         printf("%d\n",dinic(1,n));
79     }
80     return 0;
81 }