【luogu P3376 网络最大流】 模板

题目链接：https://www.luogu.org/problemnew/show/P3376

 #include <iostream>
 #include <cstdio>
 #include <algorithm>
 #include <queue>
 #include <cstring>
 using namespace std;
 const int inf = 1e9;
 const int maxn = ;
 int n, m, s, t, deep[maxn], maxflow;
 struct EDG{
     int next, to, flow;
 }edge[maxn];
 int cnt = -, head[maxn], cur[maxn];
 queue<int> q;

 void add(int u, int v, int w, bool flag)
 {
     edge[++cnt].next = head[u];
     edge[cnt].to = v;
     if(flag) edge[cnt].flow = w;
     head[u] = cnt;
 }

 bool bfs(int s, int t)
 {
     memset(deep, 0x7f, sizeof(deep));
     while(!q.empty()) q.pop();
     for(int i = ; i <= n; i++) cur[i] = head[i];
     deep[s] = ;
     q.push(s);

     while(!q.empty())
     {
         int now = q.front(); q.pop();
         for(int i = head[now]; i != -; i = edge[i].next)
         {
             if(deep[edge[i].to] > inf && edge[i].flow)
             {
                 deep[edge[i].to] = deep[now]+;
                 q.push(edge[i].to);
             }
         }
     }
     if(deep[t] < inf) return true;
     else return false;
 }

 int dfs(int now, int t, int limit)
 {
     if(!limit || now == t) return limit;
     int flow = , f;
     for(int i = cur[now]; i != -; i = edge[i].next)
     {
         cur[now] = i;
         if(deep[edge[i].to] == deep[now]+ && (f = dfs(edge[i].to, t, min(limit, edge[i].flow))))
         {
             flow += f;
             limit -= f;
             edge[i].flow -= f;
             edge[i^].flow += f;
             if(!limit) break;
         }
     }
     return flow;
 }
 void Dinic(int s, int t)
 {
     while(bfs(s,t))
     maxflow += dfs(s,t,inf);
 }
 int main()
 {
     memset(head, -, sizeof(head));
     scanf("%d%d%d%d",&n,&m,&s,&t);
     for(int i = ; i <= m; i++)
     {
         int u, v, w;
         scanf("%d%d%d",&u,&v,&w);
         add(u,v,w,);
         add(v,u,w,);
     }
     Dinic(s,t);
     printf("%d",maxflow);
     return ;
 }