最大流Dinic算法模板

#include<bits/stdc++.h>
#define int long long
using namespace std;
const int maxn = 1e5+10;
const int inf = 0x3f3f3f3f;
int n,m,s,t,tol,head[maxn],dep[maxn];
struct Edge
{
    int v,w,nxt;
}E[maxn];
void add_edge(int u,int v,int w)
{
    E[tol] = Edge{v,w,head[u]};
    head[u] = tol++;
}
bool Bfs()
{
    memset(dep,0, sizeof(dep));
    queue<int>q;
    while(!q.empty())
        q.pop();
    q.push(s);
    dep[s] = 1;
    while(!q.empty())
    {
        int u = q.front();
        q.pop();
        for(int i = head[u];i != -1;i = E[i].nxt)
        {
            if(E[i].w && !dep[E[i].v])
            {
                dep[E[i].v] = dep[u] + 1;
                q.push(E[i].v);
                if(E[i].v == t)
                    return true;
            }
        }
    }
    return false;
}
int Dfs(int u,int f)
{
    if(u == t)
        return f;
    int used = 0,d = 0;
    for(int i = head[u];i != -1;i = E[i].nxt)
    {
        if(dep[u] == dep[E[i].v] - 1 && E[i].w)
        {
            if((d = Dfs(E[i].v,min(f - used,E[i].w))))
            {
                used += d;
                E[i].w -= d;
                E[i^1].w += d;
            }
        }
    }
    if(!used)
        dep[u] = 0;
    return used;
}
int Dinic()
{
    int max_flow = 0,d;
    while(Bfs())
    {
        while((d = Dfs(s,inf)))
            max_flow += d;
    }
    return max_flow;
}
signed main()
{
    //freopen("in","r",stdin);
    ios::sync_with_stdio(false);
    cin.tie(0);
    memset(head,-1, sizeof(head));
    cin >> n >> m >> s >> t;
    int u,v,c;
    for(int i = 0;i < m; i++)
    {
        cin >> u >> v >> c;
        add_edge(u,v,c);
        add_edge(v,u,0);
    }
    cout << Dinic() << endl;
    return 0;
}