cses/cses_1694.cpp at main · EzElephant/cses · GitHub

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#include <bits/extc++.h>
using namespace std;
typedef long long ll;

template <typename T>
struct DINIC
{
    static const int MAXN = 1087;
    static const T INF = INT_MAX;
    int n, LV[MAXN], cur[MAXN];
    struct edge
    {
        int v, pre;
        T cap, r;
        edge(int v, int pre, T cap) : v(v), pre(pre), cap(cap), r(cap) {}
    };
    int g[MAXN];
    vector<edge> e;
    void init(int _n)
    {
        memset(g, -1, sizeof(int) * ((n = _n) + 1));
        e.clear();
    }
    void add_edge(int u, int v, T cap, bool directed = false)
    {
        e.push_back(edge(v, g[u], cap));
        g[u] = e.size() - 1;
        e.push_back(edge(u, g[v], directed ? 0 : cap));
        g[v] = e.size() - 1;
    }
    int bfs(int s, int t)
    {
        memset(LV, 0, sizeof(int) * (n + 1));
        memcpy(cur, g, sizeof(int) * (n + 1));
        queue<int> q;
        q.push(s);
        LV[s] = 1;
        while (q.size())
        {
            int u = q.front();
            q.pop();
            for (int i = g[u]; ~i; i = e[i].pre)
            {
                if (!LV[e[i].v] && e[i].r)
                {
                    LV[e[i].v] = LV[u] + 1;
                    q.push(e[i].v);
                    if (e[i].v == t)
                        return 1;
                }
            }
        }
        return 0;
    }
    T dfs(int u, int t, T CF = INF)
    {
        if (u == t)
            return CF;
        T df;
        for (int &i = cur[u]; ~i; i = e[i].pre)
        {
            if (LV[e[i].v] == LV[u] + 1 && e[i].r)
            {
                if (df = dfs(e[i].v, t, min(CF, e[i].r)))
                {
                    e[i].r -= df;
                    e[i ^ 1].r += df;
                    return df;
                }
            }
        }
        return LV[u] = 0;
    }
    T dinic(int s, int t, bool clean = true)
    {
        if (clean)
            for (size_t i = 0; i < e.size(); ++i)
                e[i].r = e[i].cap;
        T ans = 0, f = 0;
        while (bfs(s, t))
            while (f = dfs(s, t))
                ans += f;
        return ans;
    }
};

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    int n, m;
    DINIC<ll> d;
    cin >> n >> m;
    d.init(n);
    while (m--)
    {
        ll u, v, w;
        cin >> u >> v >> w;
        d.add_edge(u, v, w, true);
    }
    cout << d.dinic(1, n) << '\n';

    return 0;
}