Dinic C++

// taken from https://cp-algorithms.com/graph/dinic.html
#include <iostream>
#include <vector>
#include <queue>

using namespace std;

struct FlowEdge {
    int v, u;
    long long cap, flow = 0;
    FlowEdge(int v, int u, long long cap) : v(v), u(u), cap(cap) {}
};

struct Dinic {
    const long long flow_inf = 1e18;
    vector<FlowEdge> edges;
    vector<vector<int>> adj;
    int n, m = 0;
    int s, t;
    vector<int> level, ptr;
    queue<int> q;

    Dinic(int n, int s, int t) : n(n), s(s), t(t) {
        adj.resize(n);
        level.resize(n);
        ptr.resize(n);
    }

    void add_edge(int v, int u, long long cap) {
        edges.emplace_back(v, u, cap);
        edges.emplace_back(u, v, 0);
        adj[v].push_back(m);
        adj[u].push_back(m + 1);
        m += 2;
    }

    bool bfs() {
        while (!q.empty()) {
            int v = q.front();
            q.pop();
            for (int id : adj[v]) {
                if (edges[id].cap - edges[id].flow < 1)
                    continue;
                if (level[edges[id].u] != -1)
                    continue;
                level[edges[id].u] = level[v] + 1;
                q.push(edges[id].u);
            }
        }
        return level[t] != -1;
    }

    long long dfs(int v, long long pushed) {
        if (pushed == 0)
            return 0;
        if (v == t)
            return pushed;
        for (int& cid = ptr[v]; cid < (int)adj[v].size(); cid++) {
            int id = adj[v][cid];
            int u = edges[id].u;
            if (level[v] + 1 != level[u] || edges[id].cap - edges[id].flow < 1)
                continue;
            long long tr = dfs(u, min(pushed, edges[id].cap - edges[id].flow));
            if (tr == 0)
                continue;
            edges[id].flow += tr;
            edges[id ^ 1].flow -= tr;
            return tr;
        }
        return 0;
    }

    long long flow() {
        long long f = 0;
        while (true) {
            fill(level.begin(), level.end(), -1);           // reset level assignments
            level[s] = 0;                                   // source level is 0
            q.push(s);                                      // push s to bfs queue
            if (!bfs())                                     // if dist(t)=INF, we are done
                break;
            fill(ptr.begin(), ptr.end(), 0);                // pointers speed up DFS, read more at cp-algorithms.com/graph/dinic.html
            while (long long pushed = dfs(s, flow_inf)) {   // while we can find a valid path, augment it and ...
                f += pushed;                                // ... increment max flow
            }
        }
        return f;
    }
};

int main()
{
    Dinic mf(6,0,5);
    mf.add_edge(0,1,10);
    mf.add_edge(0,2,10);
    mf.add_edge(1,2,2);
    mf.add_edge(1,3,4);
    mf.add_edge(1,4,8);
    mf.add_edge(2,4,9);
    mf.add_edge(3,5,10);
    mf.add_edge(4,3,6);
    mf.add_edge(4,5,10);

    cout << "Max Flow: " << mf.flow() << '\n';
}